[GIT PULL] Introduce housekeeping subsystem v4

[GIT PULL] Introduce housekeeping subsystem v4

[Frederic Weisbecker]

Ingo,

Please pull the core/isolation-v4 branch that can be found at:

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	core/isolation-v4

HEAD: cf4c55aad44251369c8507c3823f9f9c51d4dc77

Summary of changes:

* Move the housekeeping code that was tied to NO_HZ to its own subsystem.
  Currently NO_HZ governs the other isolation features which is not right
  as dynticks is just an isolation feature like the others. We want to
  centralize the CPU isolation decisions to a subsystem of its own instead.

* Integrate isolcpus code to housekeeping and treat it as a CPU isolation
  feature.

* Reuse the "isolcpus=" kernel parameter to control the CPU isolation.
  For now only tick and domains can be isolated after this patchset:

       isolcpus=1-7         # isolate domains on CPU range 1 to 7
                            # "domain" flag is implicit by default to
                            # keep the current behaviour
                            
       isolcpus=domain,1-7  # do the same

       isolcpus=nohz,1-7    # apply nohz_full to CPU range 1 to 7

       isolcpus=nohz,domain,1-7  # apply nohz_full and isolate domains of
                                 # CPU range 1 to 7

Thanks,
	Frederic
---

Frederic Weisbecker (12):
      housekeeping: Move housekeeping related code to its own file
      watchdog: Use housekeeping_cpumask() instead of ad-hoc version
      housekeeping: Provide a dynamic off-case to housekeeping_any_cpu()
      housekeeping: Make housekeeping cpumask private
      housekeeping: Use its own static key
      housekeeping: Rename is_housekeeping_cpu to housekeeping_cpu
      housekeeping: Move it under its own config, independant from NO_HZ
      housekeeping: Introduce housekeeping flags
      housekeeping: Handle nohz_full= parameter
      housekeeping: Move isolcpus to housekeeping
      housekeeping: Add basic isolcpus flags
      housekeeping: Document isolcpus flags


 Documentation/admin-guide/kernel-parameters.txt |  33 +++---
 drivers/base/cpu.c                              |  11 +-
 drivers/net/ethernet/tile/tilegx.c              |   6 +-
 include/linux/housekeeping.h                    |  51 ++++++++
 include/linux/sched.h                           |   2 -
 include/linux/tick.h                            |  39 +------
 init/Kconfig                                    |   7 ++
 init/main.c                                     |   2 +
 kernel/Makefile                                 |   1 +
 kernel/cgroup/cpuset.c                          |  15 +--
 kernel/housekeeping.c                           | 149 ++++++++++++++++++++++++
 kernel/rcu/tree_plugin.h                        |   3 +-
 kernel/rcu/update.c                             |   3 +-
 kernel/sched/core.c                             |  25 +---
 kernel/sched/fair.c                             |   3 +-
 kernel/sched/topology.c                         |  24 +---
 kernel/time/tick-sched.c                        |  31 +----
 kernel/watchdog.c                               |  13 +--
 18 files changed, 276 insertions(+), 142 deletions(-)

[PATCH 01/12] housekeeping: Move housekeeping related code to its own file

[Frederic Weisbecker]

The housekeeping code is currently tied to the nohz code. As we are
planning to make housekeeping independant from it, start with moving
the relevant code to its own file.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 drivers/net/ethernet/tile/tilegx.c |  2 +-
 include/linux/housekeeping.h       | 56 ++++++++++++++++++++++++++++++++++++++
 include/linux/tick.h               | 37 -------------------------
 init/main.c                        |  2 ++
 kernel/Makefile                    |  1 +
 kernel/housekeeping.c              | 33 ++++++++++++++++++++++
 kernel/rcu/tree_plugin.h           |  1 +
 kernel/rcu/update.c                |  1 +
 kernel/sched/core.c                |  1 +
 kernel/sched/fair.c                |  1 +
 kernel/time/tick-sched.c           | 18 ------------
 kernel/watchdog.c                  |  1 +
 12 files changed, 98 insertions(+), 56 deletions(-)
 create mode 100644 include/linux/housekeeping.h
 create mode 100644 kernel/housekeeping.c

diff --git a/drivers/net/ethernet/tile/tilegx.c b/drivers/net/ethernet/tile/tilegx.c
index c00102b..8c7ef12 100644
--- a/drivers/net/ethernet/tile/tilegx.c
+++ b/drivers/net/ethernet/tile/tilegx.c
@@ -40,7 +40,7 @@
 #include <linux/tcp.h>
 #include <linux/net_tstamp.h>
 #include <linux/ptp_clock_kernel.h>
-#include <linux/tick.h>
+#include <linux/housekeeping.h>
 
 #include <asm/checksum.h>
 #include <asm/homecache.h>
diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
new file mode 100644
index 0000000..3d6a8e6
--- /dev/null
+++ b/include/linux/housekeeping.h
@@ -0,0 +1,56 @@
+#ifndef _LINUX_HOUSEKEEPING_H
+#define _LINUX_HOUSEKEEPING_H
+
+#include <linux/cpumask.h>
+#include <linux/init.h>
+#include <linux/tick.h>
+
+#ifdef CONFIG_NO_HZ_FULL
+extern cpumask_var_t housekeeping_mask;
+
+static inline int housekeeping_any_cpu(void)
+{
+	return cpumask_any_and(housekeeping_mask, cpu_online_mask);
+}
+
+extern void __init housekeeping_init(void);
+
+#else
+
+static inline int housekeeping_any_cpu(void)
+{
+	return smp_processor_id();
+}
+
+static inline void housekeeping_init(void) { }
+#endif /* CONFIG_NO_HZ_FULL */
+
+
+static inline const struct cpumask *housekeeping_cpumask(void)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	if (tick_nohz_full_enabled())
+		return housekeeping_mask;
+#endif
+	return cpu_possible_mask;
+}
+
+static inline bool is_housekeeping_cpu(int cpu)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	if (tick_nohz_full_enabled())
+		return cpumask_test_cpu(cpu, housekeeping_mask);
+#endif
+	return true;
+}
+
+static inline void housekeeping_affine(struct task_struct *t)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	if (tick_nohz_full_enabled())
+		set_cpus_allowed_ptr(t, housekeeping_mask);
+
+#endif
+}
+
+#endif /* _LINUX_HOUSEKEEPING_H */
diff --git a/include/linux/tick.h b/include/linux/tick.h
index fe01e68..68afc09 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -137,7 +137,6 @@ static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }
 #ifdef CONFIG_NO_HZ_FULL
 extern bool tick_nohz_full_running;
 extern cpumask_var_t tick_nohz_full_mask;
-extern cpumask_var_t housekeeping_mask;
 
 static inline bool tick_nohz_full_enabled(void)
 {
@@ -161,11 +160,6 @@ static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask)
 		cpumask_or(mask, mask, tick_nohz_full_mask);
 }
 
-static inline int housekeeping_any_cpu(void)
-{
-	return cpumask_any_and(housekeeping_mask, cpu_online_mask);
-}
-
 extern void tick_nohz_dep_set(enum tick_dep_bits bit);
 extern void tick_nohz_dep_clear(enum tick_dep_bits bit);
 extern void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit);
@@ -235,10 +229,6 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal,
 extern void tick_nohz_full_kick_cpu(int cpu);
 extern void __tick_nohz_task_switch(void);
 #else
-static inline int housekeeping_any_cpu(void)
-{
-	return smp_processor_id();
-}
 static inline bool tick_nohz_full_enabled(void) { return false; }
 static inline bool tick_nohz_full_cpu(int cpu) { return false; }
 static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { }
@@ -260,33 +250,6 @@ static inline void tick_nohz_full_kick_cpu(int cpu) { }
 static inline void __tick_nohz_task_switch(void) { }
 #endif
 
-static inline const struct cpumask *housekeeping_cpumask(void)
-{
-#ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_enabled())
-		return housekeeping_mask;
-#endif
-	return cpu_possible_mask;
-}
-
-static inline bool is_housekeeping_cpu(int cpu)
-{
-#ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_enabled())
-		return cpumask_test_cpu(cpu, housekeeping_mask);
-#endif
-	return true;
-}
-
-static inline void housekeeping_affine(struct task_struct *t)
-{
-#ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_enabled())
-		set_cpus_allowed_ptr(t, housekeeping_mask);
-
-#endif
-}
-
 static inline void tick_nohz_task_switch(void)
 {
 	if (tick_nohz_full_enabled())
diff --git a/init/main.c b/init/main.c
index 0ee9c686..bf138b9 100644
--- a/init/main.c
+++ b/init/main.c
@@ -46,6 +46,7 @@
 #include <linux/cgroup.h>
 #include <linux/efi.h>
 #include <linux/tick.h>
+#include <linux/housekeeping.h>
 #include <linux/interrupt.h>
 #include <linux/taskstats_kern.h>
 #include <linux/delayacct.h>
@@ -606,6 +607,7 @@ asmlinkage __visible void __init start_kernel(void)
 	early_irq_init();
 	init_IRQ();
 	tick_init();
+	housekeeping_init();
 	rcu_init_nohz();
 	init_timers();
 	hrtimers_init();
diff --git a/kernel/Makefile b/kernel/Makefile
index ed470aa..c63f893 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -109,6 +109,7 @@ obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_JUMP_LABEL) += jump_label.o
 obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o
 obj-$(CONFIG_TORTURE_TEST) += torture.o
+obj-$(CONFIG_NO_HZ_FULL) += housekeeping.o
 
 obj-$(CONFIG_HAS_IOMEM) += memremap.o
 
diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
new file mode 100644
index 0000000..b41c52e
--- /dev/null
+++ b/kernel/housekeeping.c
@@ -0,0 +1,33 @@
+/*
+ *  Housekeeping management. Manage the targets for routine code that can run on
+ *  any CPU: unbound workqueues, timers, kthreads and any offloadable work.
+ *
+ * Copyright (C) 2017 Red Hat, Inc., Frederic Weisbecker
+ *
+ */
+
+#include <linux/housekeeping.h>
+#include <linux/tick.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+
+cpumask_var_t housekeeping_mask;
+
+void __init housekeeping_init(void)
+{
+	if (!tick_nohz_full_enabled())
+		return;
+
+	if (!alloc_cpumask_var(&housekeeping_mask, GFP_KERNEL)) {
+		WARN(1, "NO_HZ: Can't allocate not-full dynticks cpumask\n");
+		cpumask_clear(tick_nohz_full_mask);
+		tick_nohz_full_running = false;
+		return;
+	}
+
+	cpumask_andnot(housekeeping_mask,
+		       cpu_possible_mask, tick_nohz_full_mask);
+
+	/* We need at least one CPU to handle housekeeping work */
+	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
+}
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index e012b9b..387e0a2 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -29,6 +29,7 @@
 #include <linux/oom.h>
 #include <linux/sched/debug.h>
 #include <linux/smpboot.h>
+#include <linux/housekeeping.h>
 #include <uapi/linux/sched/types.h>
 #include "../time/tick-internal.h"
 
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 5033b66..1c003e2 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -51,6 +51,7 @@
 #include <linux/kthread.h>
 #include <linux/tick.h>
 #include <linux/rcupdate_wait.h>
+#include <linux/housekeeping.h>
 
 #define CREATE_TRACE_POINTS
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 18a6966..b9769d1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -26,6 +26,7 @@
 #include <linux/profile.h>
 #include <linux/security.h>
 #include <linux/syscalls.h>
+#include <linux/housekeeping.h>
 
 #include <asm/switch_to.h>
 #include <asm/tlb.h>
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 70ba32e..3af0630 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -32,6 +32,7 @@
 #include <linux/mempolicy.h>
 #include <linux/migrate.h>
 #include <linux/task_work.h>
+#include <linux/housekeeping.h>
 
 #include <trace/events/sched.h>
 
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index c7a899c..9d29dee 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -165,7 +165,6 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
 
 #ifdef CONFIG_NO_HZ_FULL
 cpumask_var_t tick_nohz_full_mask;
-cpumask_var_t housekeeping_mask;
 bool tick_nohz_full_running;
 static atomic_t tick_dep_mask;
 
@@ -437,13 +436,6 @@ void __init tick_nohz_init(void)
 			return;
 	}
 
-	if (!alloc_cpumask_var(&housekeeping_mask, GFP_KERNEL)) {
-		WARN(1, "NO_HZ: Can't allocate not-full dynticks cpumask\n");
-		cpumask_clear(tick_nohz_full_mask);
-		tick_nohz_full_running = false;
-		return;
-	}
-
 	/*
 	 * Full dynticks uses irq work to drive the tick rescheduling on safe
 	 * locking contexts. But then we need irq work to raise its own
@@ -452,7 +444,6 @@ void __init tick_nohz_init(void)
 	if (!arch_irq_work_has_interrupt()) {
 		pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs\n");
 		cpumask_clear(tick_nohz_full_mask);
-		cpumask_copy(housekeeping_mask, cpu_possible_mask);
 		tick_nohz_full_running = false;
 		return;
 	}
@@ -465,9 +456,6 @@ void __init tick_nohz_init(void)
 		cpumask_clear_cpu(cpu, tick_nohz_full_mask);
 	}
 
-	cpumask_andnot(housekeeping_mask,
-		       cpu_possible_mask, tick_nohz_full_mask);
-
 	for_each_cpu(cpu, tick_nohz_full_mask)
 		context_tracking_cpu_set(cpu);
 
@@ -477,12 +465,6 @@ void __init tick_nohz_init(void)
 	WARN_ON(ret < 0);
 	pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
 		cpumask_pr_args(tick_nohz_full_mask));
-
-	/*
-	 * We need at least one CPU to handle housekeeping work such
-	 * as timekeeping, unbound timers, workqueues, ...
-	 */
-	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
 }
 #endif
 
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index f5d5202..3cc5596 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -24,6 +24,7 @@
 #include <linux/workqueue.h>
 #include <linux/sched/clock.h>
 #include <linux/sched/debug.h>
+#include <linux/housekeeping.h>
 
 #include <asm/irq_regs.h>
 #include <linux/kvm_para.h>
-- 
2.7.4

[PATCH 02/12] watchdog: Use housekeeping_cpumask() instead of ad-hoc version

[Frederic Weisbecker]

While trying to disable the watchog on nohz_full CPUs, the watchdog
implements an ad-hoc version of housekeeping_cpumask(). Lets replace
those re-invented lines.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 kernel/watchdog.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index 3cc5596..e672752 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -942,15 +942,10 @@ void __init lockup_detector_init(void)
 {
 	set_sample_period();
 
-#ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_enabled()) {
+	if (tick_nohz_full_enabled())
 		pr_info("Disabling watchdog on nohz_full cores by default\n");
-		cpumask_copy(&watchdog_cpumask, housekeeping_mask);
-	} else
-		cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
-#else
-	cpumask_copy(&watchdog_cpumask, cpu_possible_mask);
-#endif
+
+	cpumask_copy(&watchdog_cpumask, housekeeping_cpumask());
 
 	if (watchdog_enabled)
 		watchdog_enable_all_cpus();
-- 
2.7.4

[PATCH 03/12] housekeeping: Provide a dynamic off-case to housekeeping_any_cpu()

[Frederic Weisbecker]

housekeeping_any_cpu() doesn't handle correctly the case where
CONFIG_NO_HZ_FULL=y and no CPU is in nohz_full mode. So far no caller
needs this but let's prepare to avoid any future surprise.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 include/linux/housekeeping.h | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index 3d6a8e6..64d0ee5 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -7,24 +7,19 @@
 
 #ifdef CONFIG_NO_HZ_FULL
 extern cpumask_var_t housekeeping_mask;
-
-static inline int housekeeping_any_cpu(void)
-{
-	return cpumask_any_and(housekeeping_mask, cpu_online_mask);
-}
-
 extern void __init housekeeping_init(void);
-
 #else
-
-static inline int housekeeping_any_cpu(void)
-{
-	return smp_processor_id();
-}
-
 static inline void housekeeping_init(void) { }
 #endif /* CONFIG_NO_HZ_FULL */
 
+static inline int housekeeping_any_cpu(void)
+{
+#ifdef CONFIG_NO_HZ_FULL
+	if (tick_nohz_full_enabled())
+		return cpumask_any_and(housekeeping_mask, cpu_online_mask);
+#endif
+	return smp_processor_id();
+}
 
 static inline const struct cpumask *housekeeping_cpumask(void)
 {
-- 
2.7.4

[PATCH 04/12] housekeeping: Make housekeeping cpumask private

[Frederic Weisbecker]

Nobody needs to access this detail. housekeeping_cpumask() already
takes care about it.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 include/linux/housekeeping.h | 31 ++++++++++---------------------
 kernel/housekeeping.c        | 33 ++++++++++++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 22 deletions(-)

diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index 64d0ee5..31a1401 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -6,46 +6,35 @@
 #include <linux/tick.h>
 
 #ifdef CONFIG_NO_HZ_FULL
-extern cpumask_var_t housekeeping_mask;
+extern int housekeeping_any_cpu(void);
+extern const struct cpumask *housekeeping_cpumask(void);
+extern void housekeeping_affine(struct task_struct *t);
+extern bool housekeeping_test_cpu(int cpu);
 extern void __init housekeeping_init(void);
+
 #else
-static inline void housekeeping_init(void) { }
-#endif /* CONFIG_NO_HZ_FULL */
 
 static inline int housekeeping_any_cpu(void)
 {
-#ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_enabled())
-		return cpumask_any_and(housekeeping_mask, cpu_online_mask);
-#endif
 	return smp_processor_id();
 }
 
 static inline const struct cpumask *housekeeping_cpumask(void)
 {
-#ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_enabled())
-		return housekeeping_mask;
-#endif
 	return cpu_possible_mask;
 }
 
+static inline void housekeeping_affine(struct task_struct *t) { }
+static inline void housekeeping_init(void) { }
+#endif /* CONFIG_NO_HZ_FULL */
+
 static inline bool is_housekeeping_cpu(int cpu)
 {
 #ifdef CONFIG_NO_HZ_FULL
 	if (tick_nohz_full_enabled())
-		return cpumask_test_cpu(cpu, housekeeping_mask);
+		return housekeeping_test_cpu(cpu);
 #endif
 	return true;
 }
 
-static inline void housekeeping_affine(struct task_struct *t)
-{
-#ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_enabled())
-		set_cpus_allowed_ptr(t, housekeeping_mask);
-
-#endif
-}
-
 #endif /* _LINUX_HOUSEKEEPING_H */
diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
index b41c52e..0e70dc8 100644
--- a/kernel/housekeeping.c
+++ b/kernel/housekeeping.c
@@ -11,7 +11,38 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 
-cpumask_var_t housekeeping_mask;
+static cpumask_var_t housekeeping_mask;
+
+int housekeeping_any_cpu(void)
+{
+	if (tick_nohz_full_enabled())
+		return cpumask_any_and(housekeeping_mask, cpu_online_mask);
+
+	return smp_processor_id();
+}
+
+const struct cpumask *housekeeping_cpumask(void)
+{
+	if (tick_nohz_full_enabled())
+		return housekeeping_mask;
+
+	return cpu_possible_mask;
+}
+
+void housekeeping_affine(struct task_struct *t)
+{
+	if (tick_nohz_full_enabled())
+		set_cpus_allowed_ptr(t, housekeeping_mask);
+}
+
+bool housekeeping_test_cpu(int cpu)
+{
+	if (tick_nohz_full_enabled())
+		return cpumask_test_cpu(cpu, housekeeping_mask);
+
+	return true;
+}
+
 
 void __init housekeeping_init(void)
 {
-- 
2.7.4

[PATCH 05/12] housekeeping: Use its own static key

[Frederic Weisbecker]

Housekeeping code still depends on nohz_full static key. Since we want
to decouple housekeeping from nohz, let's create a housekeeping own static
key. It's mostly relevant for calls to is_housekeeping_cpu() from the
scheduler.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 include/linux/housekeeping.h |  3 ++-
 kernel/housekeeping.c        | 14 +++++++++-----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index 31a1401..cbe8d63 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -6,6 +6,7 @@
 #include <linux/tick.h>
 
 #ifdef CONFIG_NO_HZ_FULL
+DECLARE_STATIC_KEY_FALSE(housekeeping_overriden);
 extern int housekeeping_any_cpu(void);
 extern const struct cpumask *housekeeping_cpumask(void);
 extern void housekeeping_affine(struct task_struct *t);
@@ -31,7 +32,7 @@ static inline void housekeeping_init(void) { }
 static inline bool is_housekeeping_cpu(int cpu)
 {
 #ifdef CONFIG_NO_HZ_FULL
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		return housekeeping_test_cpu(cpu);
 #endif
 	return true;
diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
index 0e70dc8..272c344 100644
--- a/kernel/housekeeping.c
+++ b/kernel/housekeeping.c
@@ -10,12 +10,15 @@
 #include <linux/tick.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/static_key.h>
 
+DEFINE_STATIC_KEY_FALSE(housekeeping_overriden);
+EXPORT_SYMBOL_GPL(housekeeping_overriden);
 static cpumask_var_t housekeeping_mask;
 
 int housekeeping_any_cpu(void)
 {
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		return cpumask_any_and(housekeeping_mask, cpu_online_mask);
 
 	return smp_processor_id();
@@ -23,7 +26,7 @@ int housekeeping_any_cpu(void)
 
 const struct cpumask *housekeeping_cpumask(void)
 {
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		return housekeeping_mask;
 
 	return cpu_possible_mask;
@@ -31,19 +34,18 @@ const struct cpumask *housekeeping_cpumask(void)
 
 void housekeeping_affine(struct task_struct *t)
 {
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		set_cpus_allowed_ptr(t, housekeeping_mask);
 }
 
 bool housekeeping_test_cpu(int cpu)
 {
-	if (tick_nohz_full_enabled())
+	if (static_branch_unlikely(&housekeeping_overriden))
 		return cpumask_test_cpu(cpu, housekeeping_mask);
 
 	return true;
 }
 
-
 void __init housekeeping_init(void)
 {
 	if (!tick_nohz_full_enabled())
@@ -59,6 +61,8 @@ void __init housekeeping_init(void)
 	cpumask_andnot(housekeeping_mask,
 		       cpu_possible_mask, tick_nohz_full_mask);
 
+	static_branch_enable(&housekeeping_overriden);
+
 	/* We need at least one CPU to handle housekeeping work */
 	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
 }
-- 
2.7.4

[PATCH 06/12] housekeeping: Rename is_housekeeping_cpu to housekeeping_cpu

[Frederic Weisbecker]

To keep a proper housekeeping namespace.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 include/linux/housekeeping.h | 2 +-
 kernel/sched/core.c          | 6 +++---
 kernel/sched/fair.c          | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index cbe8d63..320cc2b 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -29,7 +29,7 @@ static inline void housekeeping_affine(struct task_struct *t) { }
 static inline void housekeeping_init(void) { }
 #endif /* CONFIG_NO_HZ_FULL */
 
-static inline bool is_housekeeping_cpu(int cpu)
+static inline bool housekeeping_cpu(int cpu)
 {
 #ifdef CONFIG_NO_HZ_FULL
 	if (static_branch_unlikely(&housekeeping_overriden))
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b9769d1..ec30a98 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -527,7 +527,7 @@ int get_nohz_timer_target(void)
 	int i, cpu = smp_processor_id();
 	struct sched_domain *sd;
 
-	if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu))
+	if (!idle_cpu(cpu) && housekeeping_cpu(cpu))
 		return cpu;
 
 	rcu_read_lock();
@@ -536,14 +536,14 @@ int get_nohz_timer_target(void)
 			if (cpu == i)
 				continue;
 
-			if (!idle_cpu(i) && is_housekeeping_cpu(i)) {
+			if (!idle_cpu(i) && housekeeping_cpu(i)) {
 				cpu = i;
 				goto unlock;
 			}
 		}
 	}
 
-	if (!is_housekeeping_cpu(cpu))
+	if (!housekeeping_cpu(cpu))
 		cpu = housekeeping_any_cpu();
 unlock:
 	rcu_read_unlock();
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 3af0630..43c4092 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8741,7 +8741,7 @@ void nohz_balance_enter_idle(int cpu)
 		return;
 
 	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
-	if (!is_housekeeping_cpu(cpu))
+	if (!housekeeping_cpu(cpu))
 		return;
 
 	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
-- 
2.7.4

[PATCH 07/12] housekeeping: Move it under its own config, independant from NO_HZ

[Frederic Weisbecker]

Split housekeeping config from CONFIG_NO_HZ_FULL. This way we finally
separate the isolation code from nohz.

Although a dependency to CONFIG_NO_HZ_FULL remains for now until the
housekeeping code doesn't deal anymore with nohz internals directly.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 include/linux/housekeeping.h | 6 +++---
 init/Kconfig                 | 8 ++++++++
 kernel/Makefile              | 2 +-
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index 320cc2b..dcbec47 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -5,7 +5,7 @@
 #include <linux/init.h>
 #include <linux/tick.h>
 
-#ifdef CONFIG_NO_HZ_FULL
+#ifdef CONFIG_CPU_ISOLATION
 DECLARE_STATIC_KEY_FALSE(housekeeping_overriden);
 extern int housekeeping_any_cpu(void);
 extern const struct cpumask *housekeeping_cpumask(void);
@@ -27,11 +27,11 @@ static inline const struct cpumask *housekeeping_cpumask(void)
 
 static inline void housekeeping_affine(struct task_struct *t) { }
 static inline void housekeeping_init(void) { }
-#endif /* CONFIG_NO_HZ_FULL */
+#endif /* CONFIG_CPU_ISOLATION */
 
 static inline bool housekeeping_cpu(int cpu)
 {
-#ifdef CONFIG_NO_HZ_FULL
+#ifdef CONFIG_CPU_ISOLATION
 	if (static_branch_unlikely(&housekeeping_overriden))
 		return housekeeping_test_cpu(cpu);
 #endif
diff --git a/init/Kconfig b/init/Kconfig
index 78cb246..6f52e6f 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -472,6 +472,14 @@ config TASK_IO_ACCOUNTING
 
 endmenu # "CPU/Task time and stats accounting"
 
+config CPU_ISOLATION
+	bool "CPU isolation"
+	depends on NO_HZ_FULL
+	help
+	  Make sure that CPUs running critical tasks are not disturbed by
+	  any source of "noise" such as unbound workqueues, timers, kthreads...
+	  Unbound jobs get offloaded to housekeeping CPUs.
+
 source "kernel/rcu/Kconfig"
 
 config BUILD_BIN2C
diff --git a/kernel/Makefile b/kernel/Makefile
index c63f893..5b01feb 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -109,7 +109,7 @@ obj-$(CONFIG_CRASH_DUMP) += crash_dump.o
 obj-$(CONFIG_JUMP_LABEL) += jump_label.o
 obj-$(CONFIG_CONTEXT_TRACKING) += context_tracking.o
 obj-$(CONFIG_TORTURE_TEST) += torture.o
-obj-$(CONFIG_NO_HZ_FULL) += housekeeping.o
+obj-$(CONFIG_CPU_ISOLATION) += housekeeping.o
 
 obj-$(CONFIG_HAS_IOMEM) += memremap.o
 
-- 
2.7.4

[PATCH 08/12] housekeeping: Introduce housekeeping flags

[Frederic Weisbecker]

Before we implement isolcpus under housekeeping, we need the isolation
features to be more finegrained. For example some people want nohz_full
without the full scheduler isolation, others want full scheduler
isolation without nohz_full.

So let's cut all these isolation features piecewise, at the risk of
overcutting it right now. We can still merge some flags later if they
always make sense together.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 drivers/net/ethernet/tile/tilegx.c |  4 ++--
 include/linux/housekeeping.h       | 26 +++++++++++++++++---------
 kernel/housekeeping.c              | 26 +++++++++++++++-----------
 kernel/rcu/tree_plugin.h           |  2 +-
 kernel/rcu/update.c                |  2 +-
 kernel/sched/core.c                |  8 ++++----
 kernel/sched/fair.c                |  2 +-
 kernel/watchdog.c                  |  3 ++-
 8 files changed, 43 insertions(+), 30 deletions(-)

diff --git a/drivers/net/ethernet/tile/tilegx.c b/drivers/net/ethernet/tile/tilegx.c
index 8c7ef12..831f2db 100644
--- a/drivers/net/ethernet/tile/tilegx.c
+++ b/drivers/net/ethernet/tile/tilegx.c
@@ -2270,8 +2270,8 @@ static int __init tile_net_init_module(void)
 		tile_net_dev_init(name, mac);
 
 	if (!network_cpus_init())
-		cpumask_and(&network_cpus_map, housekeeping_cpumask(),
-			    cpu_online_mask);
+		cpumask_and(&network_cpus_map,
+			    housekeeping_cpumask(HK_FLAG_MISC), cpu_online_mask);
 
 	return 0;
 }
diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index dcbec47..b1a62544 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -5,35 +5,43 @@
 #include <linux/init.h>
 #include <linux/tick.h>
 
+enum hk_flags {
+	HK_FLAG_TIMER		= 1,
+	HK_FLAG_RCU		= (1 << 1),
+	HK_FLAG_MISC		= (1 << 2),
+	HK_FLAG_SCHED		= (1 << 3),
+};
+
 #ifdef CONFIG_CPU_ISOLATION
 DECLARE_STATIC_KEY_FALSE(housekeeping_overriden);
-extern int housekeeping_any_cpu(void);
-extern const struct cpumask *housekeeping_cpumask(void);
-extern void housekeeping_affine(struct task_struct *t);
-extern bool housekeeping_test_cpu(int cpu);
+extern int housekeeping_any_cpu(enum hk_flags flags);
+extern const struct cpumask *housekeeping_cpumask(enum hk_flags flags);
+extern void housekeeping_affine(struct task_struct *t, enum hk_flags flags);
+extern bool housekeeping_test_cpu(int cpu, enum hk_flags flags);
 extern void __init housekeeping_init(void);
 
 #else
 
-static inline int housekeeping_any_cpu(void)
+static inline int housekeeping_any_cpu(enum hk_flags flags)
 {
 	return smp_processor_id();
 }
 
-static inline const struct cpumask *housekeeping_cpumask(void)
+static inline const struct cpumask *housekeeping_cpumask(enum hk_flags flags)
 {
 	return cpu_possible_mask;
 }
 
-static inline void housekeeping_affine(struct task_struct *t) { }
+static inline void housekeeping_affine(struct task_struct *t,
+				       enum hk_flags flags) { }
 static inline void housekeeping_init(void) { }
 #endif /* CONFIG_CPU_ISOLATION */
 
-static inline bool housekeeping_cpu(int cpu)
+static inline bool housekeeping_cpu(int cpu, enum hk_flags flags)
 {
 #ifdef CONFIG_CPU_ISOLATION
 	if (static_branch_unlikely(&housekeeping_overriden))
-		return housekeeping_test_cpu(cpu);
+		return housekeeping_test_cpu(cpu, flags);
 #endif
 	return true;
 }
diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
index 272c344..2cf52ee 100644
--- a/kernel/housekeeping.c
+++ b/kernel/housekeeping.c
@@ -15,34 +15,36 @@
 DEFINE_STATIC_KEY_FALSE(housekeeping_overriden);
 EXPORT_SYMBOL_GPL(housekeeping_overriden);
 static cpumask_var_t housekeeping_mask;
+static unsigned int housekeeping_flags;
 
-int housekeeping_any_cpu(void)
+int housekeeping_any_cpu(enum hk_flags flags)
 {
 	if (static_branch_unlikely(&housekeeping_overriden))
-		return cpumask_any_and(housekeeping_mask, cpu_online_mask);
-
+		if (housekeeping_flags & flags)
+			return cpumask_any_and(housekeeping_mask, cpu_online_mask);
 	return smp_processor_id();
 }
 
-const struct cpumask *housekeeping_cpumask(void)
+const struct cpumask *housekeeping_cpumask(enum hk_flags flags)
 {
 	if (static_branch_unlikely(&housekeeping_overriden))
-		return housekeeping_mask;
-
+		if (housekeeping_flags & flags)
+			return housekeeping_mask;
 	return cpu_possible_mask;
 }
 
-void housekeeping_affine(struct task_struct *t)
+void housekeeping_affine(struct task_struct *t, enum hk_flags flags)
 {
 	if (static_branch_unlikely(&housekeeping_overriden))
-		set_cpus_allowed_ptr(t, housekeeping_mask);
+		if (housekeeping_flags & flags)
+			set_cpus_allowed_ptr(t, housekeeping_mask);
 }
 
-bool housekeeping_test_cpu(int cpu)
+bool housekeeping_test_cpu(int cpu, enum hk_flags flags)
 {
 	if (static_branch_unlikely(&housekeeping_overriden))
-		return cpumask_test_cpu(cpu, housekeeping_mask);
-
+		if (housekeeping_flags & flags)
+			return cpumask_test_cpu(cpu, housekeeping_mask);
 	return true;
 }
 
@@ -61,6 +63,8 @@ void __init housekeeping_init(void)
 	cpumask_andnot(housekeeping_mask,
 		       cpu_possible_mask, tick_nohz_full_mask);
 
+	housekeeping_flags = HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
+
 	static_branch_enable(&housekeeping_overriden);
 
 	/* We need at least one CPU to handle housekeeping work */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 387e0a2..e55ff70 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -2584,7 +2584,7 @@ static void rcu_bind_gp_kthread(void)
 
 	if (!tick_nohz_full_enabled())
 		return;
-	housekeeping_affine(current);
+	housekeeping_affine(current, HK_FLAG_RCU);
 }
 
 /* Record the current task on dyntick-idle entry. */
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 1c003e2..f9df98e 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -719,7 +719,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 	LIST_HEAD(rcu_tasks_holdouts);
 
 	/* Run on housekeeping CPUs by default.  Sysadm can move if desired. */
-	housekeeping_affine(current);
+	housekeeping_affine(current, HK_FLAG_RCU);
 
 	/*
 	 * Each pass through the following loop makes one check for
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ec30a98..4b2c6ce 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -527,7 +527,7 @@ int get_nohz_timer_target(void)
 	int i, cpu = smp_processor_id();
 	struct sched_domain *sd;
 
-	if (!idle_cpu(cpu) && housekeeping_cpu(cpu))
+	if (!idle_cpu(cpu) && housekeeping_cpu(cpu, HK_FLAG_TIMER))
 		return cpu;
 
 	rcu_read_lock();
@@ -536,15 +536,15 @@ int get_nohz_timer_target(void)
 			if (cpu == i)
 				continue;
 
-			if (!idle_cpu(i) && housekeeping_cpu(i)) {
+			if (!idle_cpu(i) && housekeeping_cpu(i, HK_FLAG_TIMER)) {
 				cpu = i;
 				goto unlock;
 			}
 		}
 	}
 
-	if (!housekeeping_cpu(cpu))
-		cpu = housekeeping_any_cpu();
+	if (!housekeeping_cpu(cpu, HK_FLAG_TIMER))
+		cpu = housekeeping_any_cpu(HK_FLAG_TIMER);
 unlock:
 	rcu_read_unlock();
 	return cpu;
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 43c4092..0c1564c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8741,7 +8741,7 @@ void nohz_balance_enter_idle(int cpu)
 		return;
 
 	/* Spare idle load balancing on CPUs that don't want to be disturbed: */
-	if (!housekeeping_cpu(cpu))
+	if (!housekeeping_cpu(cpu, HK_FLAG_SCHED))
 		return;
 
 	if (test_bit(NOHZ_TICK_STOPPED, nohz_flags(cpu)))
diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index e672752..0bb7c74 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -945,7 +945,8 @@ void __init lockup_detector_init(void)
 	if (tick_nohz_full_enabled())
 		pr_info("Disabling watchdog on nohz_full cores by default\n");
 
-	cpumask_copy(&watchdog_cpumask, housekeeping_cpumask());
+	cpumask_copy(&watchdog_cpumask,
+		     housekeeping_cpumask(HK_FLAG_TIMER));
 
 	if (watchdog_enabled)
 		watchdog_enable_all_cpus();
-- 
2.7.4

[PATCH 09/12] housekeeping: Handle nohz_full= parameter

[Frederic Weisbecker]

We want to centralize the isolation management from the housekeeping
subsystem. Therefore we need to handle the nohz_full= parameter from
there.

Since nohz_full= so far has involved unbound timers, watchdog, RCU
and tilegx NAPI isolation, we keep that default behaviour.

nohz_full= is deemed to be deprecated in the future. We want to control
the isolation features from the isolcpus= parameter.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 include/linux/housekeeping.h |  1 +
 include/linux/tick.h         |  2 ++
 init/Kconfig                 |  1 -
 kernel/housekeeping.c        | 44 +++++++++++++++++++++++++++++++-------------
 kernel/time/tick-sched.c     | 13 +++----------
 5 files changed, 37 insertions(+), 24 deletions(-)

diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index b1a62544..35fb197 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -10,6 +10,7 @@ enum hk_flags {
 	HK_FLAG_RCU		= (1 << 1),
 	HK_FLAG_MISC		= (1 << 2),
 	HK_FLAG_SCHED		= (1 << 3),
+	HK_FLAG_TICK		= (1 << 4),
 };
 
 #ifdef CONFIG_CPU_ISOLATION
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 68afc09..e2a163a 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -228,6 +228,7 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal,
 
 extern void tick_nohz_full_kick_cpu(int cpu);
 extern void __tick_nohz_task_switch(void);
+extern void __init tick_nohz_full_setup(cpumask_var_t cpumask);
 #else
 static inline bool tick_nohz_full_enabled(void) { return false; }
 static inline bool tick_nohz_full_cpu(int cpu) { return false; }
@@ -248,6 +249,7 @@ static inline void tick_dep_clear_signal(struct signal_struct *signal,
 
 static inline void tick_nohz_full_kick_cpu(int cpu) { }
 static inline void __tick_nohz_task_switch(void) { }
+static inline void tick_nohz_full_setup(cpumask_var_t cpumask) { }
 #endif
 
 static inline void tick_nohz_task_switch(void)
diff --git a/init/Kconfig b/init/Kconfig
index 6f52e6f..f8564df5 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -474,7 +474,6 @@ endmenu # "CPU/Task time and stats accounting"
 
 config CPU_ISOLATION
 	bool "CPU isolation"
-	depends on NO_HZ_FULL
 	help
 	  Make sure that CPUs running critical tasks are not disturbed by
 	  any source of "noise" such as unbound workqueues, timers, kthreads...
diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
index 2cf52ee..8fb8d6b 100644
--- a/kernel/housekeeping.c
+++ b/kernel/housekeeping.c
@@ -50,23 +50,41 @@ bool housekeeping_test_cpu(int cpu, enum hk_flags flags)
 
 void __init housekeeping_init(void)
 {
-	if (!tick_nohz_full_enabled())
+	if (!housekeeping_flags)
 		return;
 
-	if (!alloc_cpumask_var(&housekeeping_mask, GFP_KERNEL)) {
-		WARN(1, "NO_HZ: Can't allocate not-full dynticks cpumask\n");
-		cpumask_clear(tick_nohz_full_mask);
-		tick_nohz_full_running = false;
-		return;
-	}
-
-	cpumask_andnot(housekeeping_mask,
-		       cpu_possible_mask, tick_nohz_full_mask);
-
-	housekeeping_flags = HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
-
 	static_branch_enable(&housekeeping_overriden);
 
 	/* We need at least one CPU to handle housekeeping work */
 	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
 }
+
+#ifdef CONFIG_NO_HZ_FULL
+static int __init housekeeping_nohz_full_setup(char *str)
+{
+	cpumask_var_t non_housekeeping_mask;
+
+	alloc_bootmem_cpumask_var(&non_housekeeping_mask);
+	if (cpulist_parse(str, non_housekeeping_mask) < 0) {
+		pr_warn("Housekeeping: Incorrect nohz_full cpumask\n");
+		free_bootmem_cpumask_var(non_housekeeping_mask);
+		return 0;
+	}
+
+	alloc_bootmem_cpumask_var(&housekeeping_mask);
+	cpumask_andnot(housekeeping_mask, cpu_possible_mask, non_housekeeping_mask);
+
+	if (cpumask_empty(housekeeping_mask))
+		cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
+
+	housekeeping_flags = HK_FLAG_TICK | HK_FLAG_TIMER |
+				HK_FLAG_RCU | HK_FLAG_MISC;
+
+	tick_nohz_full_setup(non_housekeeping_mask);
+
+	free_bootmem_cpumask_var(non_housekeeping_mask);
+
+	return 1;
+}
+__setup("nohz_full=", housekeeping_nohz_full_setup);
+#endif
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 9d29dee..f09dd43 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -384,20 +384,13 @@ void __tick_nohz_task_switch(void)
 	local_irq_restore(flags);
 }
 
-/* Parse the boot-time nohz CPU list from the kernel parameters. */
-static int __init tick_nohz_full_setup(char *str)
+/* Get the boot-time nohz CPU list from the kernel parameters. */
+void __init tick_nohz_full_setup(cpumask_var_t cpumask)
 {
 	alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
-	if (cpulist_parse(str, tick_nohz_full_mask) < 0) {
-		pr_warn("NO_HZ: Incorrect nohz_full cpumask\n");
-		free_bootmem_cpumask_var(tick_nohz_full_mask);
-		return 1;
-	}
+	cpumask_copy(tick_nohz_full_mask, cpumask);
 	tick_nohz_full_running = true;
-
-	return 1;
 }
-__setup("nohz_full=", tick_nohz_full_setup);
 
 static int tick_nohz_cpu_down(unsigned int cpu)
 {
-- 
2.7.4

[PATCH 10/12] housekeeping: Move isolcpus to housekeeping

[Frederic Weisbecker]

We want to centralize the isolation features on the housekeeping
subsystem and scheduler domain isolation is a significant part of it.

No intended behaviour change, we just reuse the housekeeping cpumask
and core code.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 drivers/base/cpu.c           | 11 ++++++++-
 include/linux/housekeeping.h |  1 +
 include/linux/sched.h        |  2 --
 kernel/cgroup/cpuset.c       | 15 ++++--------
 kernel/housekeeping.c        | 57 +++++++++++++++++++++++++++++++++++---------
 kernel/sched/core.c          | 16 +------------
 kernel/sched/topology.c      | 24 +++++--------------
 7 files changed, 69 insertions(+), 57 deletions(-)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 321cd7b..7aa0d12 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -18,6 +18,7 @@
 #include <linux/cpufeature.h>
 #include <linux/tick.h>
 #include <linux/pm_qos.h>
+#include <linux/housekeeping.h>
 
 #include "base.h"
 
@@ -271,8 +272,16 @@ static ssize_t print_cpus_isolated(struct device *dev,
 				  struct device_attribute *attr, char *buf)
 {
 	int n = 0, len = PAGE_SIZE-2;
+	cpumask_var_t isolated;
 
-	n = scnprintf(buf, len, "%*pbl\n", cpumask_pr_args(cpu_isolated_map));
+	if (!alloc_cpumask_var(&isolated, GFP_KERNEL))
+		return -ENOMEM;
+
+	cpumask_andnot(isolated, cpu_possible_mask,
+		       housekeeping_cpumask(HK_FLAG_DOMAIN));
+	n = scnprintf(buf, len, "%*pbl\n", cpumask_pr_args(isolated));
+
+	free_cpumask_var(isolated);
 
 	return n;
 }
diff --git a/include/linux/housekeeping.h b/include/linux/housekeeping.h
index 35fb197..a99466e 100644
--- a/include/linux/housekeeping.h
+++ b/include/linux/housekeeping.h
@@ -11,6 +11,7 @@ enum hk_flags {
 	HK_FLAG_MISC		= (1 << 2),
 	HK_FLAG_SCHED		= (1 << 3),
 	HK_FLAG_TICK		= (1 << 4),
+	HK_FLAG_DOMAIN		= (1 << 5),
 };
 
 #ifdef CONFIG_CPU_ISOLATION
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 92fb8dd..962de00 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -166,8 +166,6 @@ struct task_group;
 /* Task command name length: */
 #define TASK_COMM_LEN			16
 
-extern cpumask_var_t			cpu_isolated_map;
-
 extern void scheduler_tick(void);
 
 #define	MAX_SCHEDULE_TIMEOUT		LONG_MAX
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 4657e29..4156ad9 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -57,7 +57,7 @@
 #include <linux/backing-dev.h>
 #include <linux/sort.h>
 #include <linux/oom.h>
-
+#include <linux/housekeeping.h>
 #include <linux/uaccess.h>
 #include <linux/atomic.h>
 #include <linux/mutex.h>
@@ -656,7 +656,6 @@ static int generate_sched_domains(cpumask_var_t **domains,
 	int csn;		/* how many cpuset ptrs in csa so far */
 	int i, j, k;		/* indices for partition finding loops */
 	cpumask_var_t *doms;	/* resulting partition; i.e. sched domains */
-	cpumask_var_t non_isolated_cpus;  /* load balanced CPUs */
 	struct sched_domain_attr *dattr;  /* attributes for custom domains */
 	int ndoms = 0;		/* number of sched domains in result */
 	int nslot;		/* next empty doms[] struct cpumask slot */
@@ -666,10 +665,6 @@ static int generate_sched_domains(cpumask_var_t **domains,
 	dattr = NULL;
 	csa = NULL;
 
-	if (!alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL))
-		goto done;
-	cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
-
 	/* Special case for the 99% of systems with one, full, sched domain */
 	if (is_sched_load_balance(&top_cpuset)) {
 		ndoms = 1;
@@ -683,7 +678,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
 			update_domain_attr_tree(dattr, &top_cpuset);
 		}
 		cpumask_and(doms[0], top_cpuset.effective_cpus,
-				     non_isolated_cpus);
+			    housekeeping_cpumask(HK_FLAG_DOMAIN));
 
 		goto done;
 	}
@@ -707,7 +702,8 @@ static int generate_sched_domains(cpumask_var_t **domains,
 		 */
 		if (!cpumask_empty(cp->cpus_allowed) &&
 		    !(is_sched_load_balance(cp) &&
-		      cpumask_intersects(cp->cpus_allowed, non_isolated_cpus)))
+		      cpumask_intersects(cp->cpus_allowed,
+					 housekeeping_cpumask(HK_FLAG_DOMAIN))))
 			continue;
 
 		if (is_sched_load_balance(cp))
@@ -789,7 +785,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
 
 			if (apn == b->pn) {
 				cpumask_or(dp, dp, b->effective_cpus);
-				cpumask_and(dp, dp, non_isolated_cpus);
+				cpumask_and(dp, dp, housekeeping_cpumask(HK_FLAG_DOMAIN));
 				if (dattr)
 					update_domain_attr_tree(dattr + nslot, b);
 
@@ -802,7 +798,6 @@ static int generate_sched_domains(cpumask_var_t **domains,
 	BUG_ON(nslot != ndoms);
 
 done:
-	free_cpumask_var(non_isolated_cpus);
 	kfree(csa);
 
 	/*
diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
index 8fb8d6b..30ee98f 100644
--- a/kernel/housekeeping.c
+++ b/kernel/housekeeping.c
@@ -59,32 +59,67 @@ void __init housekeeping_init(void)
 	WARN_ON_ONCE(cpumask_empty(housekeeping_mask));
 }
 
-#ifdef CONFIG_NO_HZ_FULL
-static int __init housekeeping_nohz_full_setup(char *str)
+static int __init housekeeping_setup(char *str, enum hk_flags flags)
 {
 	cpumask_var_t non_housekeeping_mask;
 
 	alloc_bootmem_cpumask_var(&non_housekeeping_mask);
 	if (cpulist_parse(str, non_housekeeping_mask) < 0) {
-		pr_warn("Housekeeping: Incorrect nohz_full cpumask\n");
+		pr_warn("Housekeeping: nohz_full= or isolcpus= incorrect CPU range\n");
 		free_bootmem_cpumask_var(non_housekeeping_mask);
 		return 0;
 	}
 
-	alloc_bootmem_cpumask_var(&housekeeping_mask);
-	cpumask_andnot(housekeeping_mask, cpu_possible_mask, non_housekeeping_mask);
+	if (!housekeeping_flags) {
+		alloc_bootmem_cpumask_var(&housekeeping_mask);
+		cpumask_andnot(housekeeping_mask,
+			       cpu_possible_mask, non_housekeeping_mask);
+		if (cpumask_empty(housekeeping_mask))
+			cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
+	} else {
+		cpumask_var_t tmp;
 
-	if (cpumask_empty(housekeeping_mask))
-		cpumask_set_cpu(smp_processor_id(), housekeeping_mask);
+		alloc_bootmem_cpumask_var(&tmp);
+		cpumask_andnot(tmp, cpu_possible_mask, non_housekeeping_mask);
+		if (!cpumask_equal(tmp, housekeeping_mask)) {
+			pr_warn("Housekeeping: nohz_full= must match isolcpus=\n");
+			free_bootmem_cpumask_var(tmp);
+			free_bootmem_cpumask_var(non_housekeeping_mask);
+			return 0;
+		}
+		free_bootmem_cpumask_var(tmp);
+	}
 
-	housekeeping_flags = HK_FLAG_TICK | HK_FLAG_TIMER |
-				HK_FLAG_RCU | HK_FLAG_MISC;
+	if ((flags & HK_FLAG_TICK) && !(housekeeping_flags & HK_FLAG_TICK)) {
+		if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {
+			tick_nohz_full_setup(non_housekeeping_mask);
+		} else {
+			pr_warn("Housekeeping: nohz unsupported."
+				" Build with CONFIG_NO_HZ_FULL\n");
+			free_bootmem_cpumask_var(non_housekeeping_mask);
+			return 0;
+		}
+	}
 
-	tick_nohz_full_setup(non_housekeeping_mask);
+	housekeeping_flags |= flags;
 
 	free_bootmem_cpumask_var(non_housekeeping_mask);
 
 	return 1;
 }
+
+static int __init housekeeping_nohz_full_setup(char *str)
+{
+	unsigned int flags;
+
+	flags = HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | HK_FLAG_MISC;
+
+	return housekeeping_setup(str, flags);
+}
 __setup("nohz_full=", housekeeping_nohz_full_setup);
-#endif
+
+static int __init housekeeping_isolcpus_setup(char *str)
+{
+	return housekeeping_setup(str, HK_FLAG_DOMAIN);
+}
+__setup("isolcpus=", housekeeping_isolcpus_setup);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4b2c6ce..be124f9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -84,9 +84,6 @@ __read_mostly int scheduler_running;
  */
 int sysctl_sched_rt_runtime = 950000;
 
-/* CPUs with isolated domains */
-cpumask_var_t cpu_isolated_map;
-
 /*
  * __task_rq_lock - lock the rq @p resides on.
  */
@@ -5705,10 +5702,6 @@ static inline void sched_init_smt(void) { }
 
 void __init sched_init_smp(void)
 {
-	cpumask_var_t non_isolated_cpus;
-
-	alloc_cpumask_var(&non_isolated_cpus, GFP_KERNEL);
-
 	sched_init_numa();
 
 	/*
@@ -5718,16 +5711,12 @@ void __init sched_init_smp(void)
 	 */
 	mutex_lock(&sched_domains_mutex);
 	sched_init_domains(cpu_active_mask);
-	cpumask_andnot(non_isolated_cpus, cpu_possible_mask, cpu_isolated_map);
-	if (cpumask_empty(non_isolated_cpus))
-		cpumask_set_cpu(smp_processor_id(), non_isolated_cpus);
 	mutex_unlock(&sched_domains_mutex);
 
 	/* Move init over to a non-isolated CPU */
-	if (set_cpus_allowed_ptr(current, non_isolated_cpus) < 0)
+	if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_FLAG_DOMAIN)) < 0)
 		BUG();
 	sched_init_granularity();
-	free_cpumask_var(non_isolated_cpus);
 
 	init_sched_rt_class();
 	init_sched_dl_class();
@@ -5931,9 +5920,6 @@ void __init sched_init(void)
 	calc_load_update = jiffies + LOAD_FREQ;
 
 #ifdef CONFIG_SMP
-	/* May be allocated at isolcpus cmdline parse time */
-	if (cpu_isolated_map == NULL)
-		zalloc_cpumask_var(&cpu_isolated_map, GFP_NOWAIT);
 	idle_thread_set_boot_cpu();
 	set_cpu_rq_start_time(smp_processor_id());
 #endif
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index f1cf4f3..c6ec01b 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -3,6 +3,7 @@
  */
 #include <linux/sched.h>
 #include <linux/mutex.h>
+#include <linux/housekeeping.h>
 
 #include "sched.h"
 
@@ -463,21 +464,6 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
 	update_top_cache_domain(cpu);
 }
 
-/* Setup the mask of CPUs configured for isolated domains */
-static int __init isolated_cpu_setup(char *str)
-{
-	int ret;
-
-	alloc_bootmem_cpumask_var(&cpu_isolated_map);
-	ret = cpulist_parse(str, cpu_isolated_map);
-	if (ret) {
-		pr_err("sched: Error, all isolcpus= values must be between 0 and %u\n", nr_cpu_ids);
-		return 0;
-	}
-	return 1;
-}
-__setup("isolcpus=", isolated_cpu_setup);
-
 struct s_data {
 	struct sched_domain ** __percpu sd;
 	struct root_domain	*rd;
@@ -1773,7 +1759,7 @@ int sched_init_domains(const struct cpumask *cpu_map)
 	doms_cur = alloc_sched_domains(ndoms_cur);
 	if (!doms_cur)
 		doms_cur = &fallback_doms;
-	cpumask_andnot(doms_cur[0], cpu_map, cpu_isolated_map);
+	cpumask_and(doms_cur[0], cpu_map, housekeeping_cpumask(HK_FLAG_DOMAIN));
 	err = build_sched_domains(doms_cur[0], NULL);
 	register_sched_domain_sysctl();
 
@@ -1856,7 +1842,8 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
 		doms_new = alloc_sched_domains(1);
 		if (doms_new) {
 			n = 1;
-			cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
+			cpumask_and(doms_new[0], cpu_active_mask,
+				    housekeeping_cpumask(HK_FLAG_DOMAIN));
 		}
 	} else {
 		n = ndoms_new;
@@ -1879,7 +1866,8 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
 	if (!doms_new) {
 		n = 0;
 		doms_new = &fallback_doms;
-		cpumask_andnot(doms_new[0], cpu_active_mask, cpu_isolated_map);
+		cpumask_and(doms_new[0], cpu_active_mask,
+			    housekeeping_cpumask(HK_FLAG_DOMAIN));
 	}
 
 	/* Build new domains: */
-- 
2.7.4

[PATCH 11/12] housekeeping: Add basic isolcpus flags

[Frederic Weisbecker]

Add flags to control nohz and domain isolations from "isolcpus=", in
order to centralize the isolation features to a common interface. Domain
isolation remains the default so not to break the existing isolcpus
boot paramater behaviour.

Further flags in the future may include 0hz (1hz tick offload) and timers,
workqueue, RCU, kthread, watchdog, likely all merged together in a
common flag ("async"?). In any case, this will have to be modifiable by
cpusets.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 kernel/housekeeping.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/kernel/housekeeping.c b/kernel/housekeeping.c
index 30ee98f..089472f 100644
--- a/kernel/housekeeping.c
+++ b/kernel/housekeeping.c
@@ -11,6 +11,7 @@
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/static_key.h>
+#include <linux/ctype.h>
 
 DEFINE_STATIC_KEY_FALSE(housekeeping_overriden);
 EXPORT_SYMBOL_GPL(housekeeping_overriden);
@@ -120,6 +121,29 @@ __setup("nohz_full=", housekeeping_nohz_full_setup);
 
 static int __init housekeeping_isolcpus_setup(char *str)
 {
-	return housekeeping_setup(str, HK_FLAG_DOMAIN);
+	unsigned int flags = 0;
+
+	while (isalpha(*str)) {
+		if (!strncmp(str, "nohz,", 5)) {
+			str += 5;
+			flags |= HK_FLAG_TICK;
+			continue;
+		}
+
+		if (!strncmp(str, "domain,", 7)) {
+			str += 7;
+			flags |= HK_FLAG_DOMAIN;
+			continue;
+		}
+
+		pr_warn("isolcpus: Error, unknown flag\n");
+		return 0;
+	}
+
+	/* Default behaviour for isolcpus without flags */
+	if (!flags)
+		flags |= HK_FLAG_DOMAIN;
+
+	return housekeeping_setup(str, flags);
 }
 __setup("isolcpus=", housekeeping_isolcpus_setup);
-- 
2.7.4

[PATCH 12/12] housekeeping: Document isolcpus flags

[Frederic Weisbecker]

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 35 +++++++++++++++----------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 0549662..34ea914 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1727,20 +1727,27 @@
 	isapnp=		[ISAPNP]
 			Format: <RDP>,<reset>,<pci_scan>,<verbosity>
 
-	isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
-			The argument is a cpu list, as described above.
-
-			This option can be used to specify one or more CPUs
-			to isolate from the general SMP balancing and scheduling
-			algorithms. You can move a process onto or off an
-			"isolated" CPU via the CPU affinity syscalls or cpuset.
-			<cpu number> begins at 0 and the maximum value is
-			"number of CPUs in system - 1".
-
-			This option is the preferred way to isolate CPUs. The
-			alternative -- manually setting the CPU mask of all
-			tasks in the system -- can cause problems and
-			suboptimal load balancer performance.
+	isolcpus=	[KNL,SMP] Isolate a given set of CPUs from disturbance.
+			Format: [flag-list,]<cpu-list>
+
+			Specify one or more CPUs to isolate from disturbances
+			specified in the flag list (default: domain):
+
+			nohz
+			  Disable the tick when a single task runs.
+			domain
+			  Isolate from the general SMP balancing and scheduling
+			  algorithms. This option is the preferred way to isolate
+			  CPUs from tasks. The alternative -- manually setting the
+			  CPU mask of all tasks in the system, can cause problems
+			  and suboptimal load balancer performance. You can move a
+			  process onto or off an "isolated" CPU via the CPU
+			  affinity syscalls or cpuset. <cpu number> begins at 0
+			  and the maximum value is "number of CPUs in system - 1".
+
+			The format of <cpu-list> is described above.
+
+
 
 	iucv=		[HW,NET]
 
-- 
2.7.4

Re: [GIT PULL] Introduce housekeeping subsystem v4

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> Ingo,
> 
> Please pull the core/isolation-v4 branch that can be found at:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
> 	core/isolation-v4
> 
> HEAD: cf4c55aad44251369c8507c3823f9f9c51d4dc77
> 
> Summary of changes:
> 
> * Move the housekeeping code that was tied to NO_HZ to its own subsystem.
>   Currently NO_HZ governs the other isolation features which is not right
>   as dynticks is just an isolation feature like the others. We want to
>   centralize the CPU isolation decisions to a subsystem of its own instead.
> 
> * Integrate isolcpus code to housekeeping and treat it as a CPU isolation
>   feature.
> 
> * Reuse the "isolcpus=" kernel parameter to control the CPU isolation.
>   For now only tick and domains can be isolated after this patchset:
> 
>        isolcpus=1-7         # isolate domains on CPU range 1 to 7
>                             # "domain" flag is implicit by default to
>                             # keep the current behaviour
>                             
>        isolcpus=domain,1-7  # do the same
> 
>        isolcpus=nohz,1-7    # apply nohz_full to CPU range 1 to 7
> 
>        isolcpus=nohz,domain,1-7  # apply nohz_full and isolate domains of
>                                  # CPU range 1 to 7
> 
> Thanks,
> 	Frederic
> ---
> 
> Frederic Weisbecker (12):
>       housekeeping: Move housekeeping related code to its own file
>       watchdog: Use housekeeping_cpumask() instead of ad-hoc version
>       housekeeping: Provide a dynamic off-case to housekeeping_any_cpu()
>       housekeeping: Make housekeeping cpumask private
>       housekeeping: Use its own static key
>       housekeeping: Rename is_housekeeping_cpu to housekeeping_cpu
>       housekeeping: Move it under its own config, independant from NO_HZ
>       housekeeping: Introduce housekeeping flags
>       housekeeping: Handle nohz_full= parameter
>       housekeeping: Move isolcpus to housekeeping
>       housekeeping: Add basic isolcpus flags
>       housekeeping: Document isolcpus flags
> 
> 
>  Documentation/admin-guide/kernel-parameters.txt |  33 +++---
>  drivers/base/cpu.c                              |  11 +-
>  drivers/net/ethernet/tile/tilegx.c              |   6 +-
>  include/linux/housekeeping.h                    |  51 ++++++++
>  include/linux/sched.h                           |   2 -
>  include/linux/tick.h                            |  39 +------
>  init/Kconfig                                    |   7 ++
>  init/main.c                                     |   2 +
>  kernel/Makefile                                 |   1 +
>  kernel/cgroup/cpuset.c                          |  15 +--
>  kernel/housekeeping.c                           | 149 ++++++++++++++++++++++++
>  kernel/rcu/tree_plugin.h                        |   3 +-
>  kernel/rcu/update.c                             |   3 +-
>  kernel/sched/core.c                             |  25 +---
>  kernel/sched/fair.c                             |   3 +-
>  kernel/sched/topology.c                         |  24 +---
>  kernel/time/tick-sched.c                        |  31 +----
>  kernel/watchdog.c                               |  13 +--
>  18 files changed, 276 insertions(+), 142 deletions(-)

Yeah, so while I agree that all this functionality needs to be factored
out and organized, I have a problem with this specific high level organization.

The main problem I think is that it's all called "housekeeping", which is pretty 
fuzzy and opaque. What does 'housekeeping' exactly mean? A dozen of details if you 
look at the code - and this name does not make it much easier to think about this 
whole problem category.

So how about introducing _two_ new high level concepts:

  1) 'global time handling'
  2) 'double async CPU callbacks'

The notion of 'global time' handling is obvious to everyone I think: it involves 
the system-global guarantee that certain kernel jobs will be executed 
periodically. At least one CPU in the system needs to handle 'global time'.

The notion of 'double async CPU callbacks' is less obvious: it involves the action 
of invoking a callback on a CPU, that might be executed on _another_ CPU.

I.e. there are 3 CPUs involved:

	- the invoking CPU
	- the target CPU
	- the CPU(s!) that will handle the callback (the housekeeping CPU mask)

For example the kmem-cache on_each_cpu() calls in mm/slab.c would fall into this 
category.

I don't know to what extent it makes sense to formalize and unify these 
facilities: it's certain that the (former) housekeeping CPU mask should be shared 
by these two facilities: the CPU executing global time callbacks periodically 
should be one of the CPUs that execute double-async CPU callbacks.

But by separating all this functionality into these two categories, it's already 
much easier to me to argue about which bit does what and why.

What do you think?

Thanks,

	Ingo

Re: [GIT PULL] Introduce housekeeping subsystem v4

[Frederic Weisbecker]

On 28/09/2017 11:54, Ingo Molnar wrote:
> 
> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
> 
>> Ingo,
>>
>> Please pull the core/isolation-v4 branch that can be found at:
>>
>> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
>> 	core/isolation-v4
>>
>> HEAD: cf4c55aad44251369c8507c3823f9f9c51d4dc77
>>
>> Summary of changes:
>>
>> * Move the housekeeping code that was tied to NO_HZ to its own subsystem.
>>    Currently NO_HZ governs the other isolation features which is not right
>>    as dynticks is just an isolation feature like the others. We want to
>>    centralize the CPU isolation decisions to a subsystem of its own instead.
>>
>> * Integrate isolcpus code to housekeeping and treat it as a CPU isolation
>>    feature.
>>
>> * Reuse the "isolcpus=" kernel parameter to control the CPU isolation.
>>    For now only tick and domains can be isolated after this patchset:
>>
>>         isolcpus=1-7         # isolate domains on CPU range 1 to 7
>>                              # "domain" flag is implicit by default to
>>                              # keep the current behaviour
>>                              
>>         isolcpus=domain,1-7  # do the same
>>
>>         isolcpus=nohz,1-7    # apply nohz_full to CPU range 1 to 7
>>
>>         isolcpus=nohz,domain,1-7  # apply nohz_full and isolate domains of
>>                                   # CPU range 1 to 7
>>
>> Thanks,
>> 	Frederic
>> ---
>>
>> Frederic Weisbecker (12):
>>        housekeeping: Move housekeeping related code to its own file
>>        watchdog: Use housekeeping_cpumask() instead of ad-hoc version
>>        housekeeping: Provide a dynamic off-case to housekeeping_any_cpu()
>>        housekeeping: Make housekeeping cpumask private
>>        housekeeping: Use its own static key
>>        housekeeping: Rename is_housekeeping_cpu to housekeeping_cpu
>>        housekeeping: Move it under its own config, independant from NO_HZ
>>        housekeeping: Introduce housekeeping flags
>>        housekeeping: Handle nohz_full= parameter
>>        housekeeping: Move isolcpus to housekeeping
>>        housekeeping: Add basic isolcpus flags
>>        housekeeping: Document isolcpus flags
>>
>>
>>   Documentation/admin-guide/kernel-parameters.txt |  33 +++---
>>   drivers/base/cpu.c                              |  11 +-
>>   drivers/net/ethernet/tile/tilegx.c              |   6 +-
>>   include/linux/housekeeping.h                    |  51 ++++++++
>>   include/linux/sched.h                           |   2 -
>>   include/linux/tick.h                            |  39 +------
>>   init/Kconfig                                    |   7 ++
>>   init/main.c                                     |   2 +
>>   kernel/Makefile                                 |   1 +
>>   kernel/cgroup/cpuset.c                          |  15 +--
>>   kernel/housekeeping.c                           | 149 ++++++++++++++++++++++++
>>   kernel/rcu/tree_plugin.h                        |   3 +-
>>   kernel/rcu/update.c                             |   3 +-
>>   kernel/sched/core.c                             |  25 +---
>>   kernel/sched/fair.c                             |   3 +-
>>   kernel/sched/topology.c                         |  24 +---
>>   kernel/time/tick-sched.c                        |  31 +----
>>   kernel/watchdog.c                               |  13 +--
>>   18 files changed, 276 insertions(+), 142 deletions(-)
> 
> Yeah, so while I agree that all this functionality needs to be factored
> out and organized, I have a problem with this specific high level organization.
> 
> The main problem I think is that it's all called "housekeeping", which is pretty
> fuzzy and opaque. What does 'housekeeping' exactly mean? A dozen of details if you
> look at the code - and this name does not make it much easier to think about this
> whole problem category.

Indeed I feel that housekeeping is probably not the best concept to 
express all these things. I'm all for something clearer.

> 
> So how about introducing _two_ new high level concepts:
> 
>    1) 'global time handling'
>    2) 'double async CPU callbacks'
> 
> The notion of 'global time' handling is obvious to everyone I think: it involves
> the system-global guarantee that certain kernel jobs will be executed
> periodically. At least one CPU in the system needs to handle 'global time'.
> 
> The notion of 'double async CPU callbacks' is less obvious: it involves the action
> of invoking a callback on a CPU, that might be executed on _another_ CPU.
> 
> I.e. there are 3 CPUs involved:
> 
> 	- the invoking CPU
> 	- the target CPU
> 	- the CPU(s!) that will handle the callback (the housekeeping CPU mask)
> 
> For example the kmem-cache on_each_cpu() calls in mm/slab.c would fall into this
> category.

Hmm, I'm not clear on this one. Do you mean works that can be executed 
concurrently?

> 
> I don't know to what extent it makes sense to formalize and unify these
> facilities: it's certain that the (former) housekeeping CPU mask should be shared
> by these two facilities: the CPU executing global time callbacks periodically
> should be one of the CPUs that execute double-async CPU callbacks.
> 
> But by separating all this functionality into these two categories, it's already
> much easier to me to argue about which bit does what and why.

Note that some housekeeping concepts may not fall into any of these 
categories. For example domain isolation.

Thanks.

> 
> What do you think?
> 
> Thanks,
> 
> 	Ingo
> 

Re: [GIT PULL] Introduce housekeeping subsystem v4

[Christopher Lameter]

On Fri, 29 Sep 2017, Frederic Weisbecker wrote:

> Indeed I feel that housekeeping is probably not the best concept to express
> all these things. I'm all for something clearer.


Hmmm some ideas:

OS maintenance tasks

Delayed maintenance

Supervisor

OS Management

Re: [GIT PULL] Introduce housekeeping subsystem v4

[Frederic Weisbecker]

2017-09-29 15:34 GMT+02:00 Frederic Weisbecker <fweisbec@gmail.com>:
> On 28/09/2017 11:54, Ingo Molnar wrote:
>>
>>
>> * Frederic Weisbecker <fweisbec@gmail.com> wrote:
>>
>>> Ingo,
>>>
>>> Please pull the core/isolation-v4 branch that can be found at:
>>>
>>> git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
>>>         core/isolation-v4
>>>
>>> HEAD: cf4c55aad44251369c8507c3823f9f9c51d4dc77
>>>
>>> Summary of changes:
>>>
>>> * Move the housekeeping code that was tied to NO_HZ to its own subsystem.
>>>    Currently NO_HZ governs the other isolation features which is not
>>> right
>>>    as dynticks is just an isolation feature like the others. We want to
>>>    centralize the CPU isolation decisions to a subsystem of its own
>>> instead.
>>>
>>> * Integrate isolcpus code to housekeeping and treat it as a CPU isolation
>>>    feature.
>>>
>>> * Reuse the "isolcpus=" kernel parameter to control the CPU isolation.
>>>    For now only tick and domains can be isolated after this patchset:
>>>
>>>         isolcpus=1-7         # isolate domains on CPU range 1 to 7
>>>                              # "domain" flag is implicit by default to
>>>                              # keep the current behaviour
>>>                                      isolcpus=domain,1-7  # do the same
>>>
>>>         isolcpus=nohz,1-7    # apply nohz_full to CPU range 1 to 7
>>>
>>>         isolcpus=nohz,domain,1-7  # apply nohz_full and isolate domains
>>> of
>>>                                   # CPU range 1 to 7
>>>
>>> Thanks,
>>>         Frederic
>>> ---
>>>
>>> Frederic Weisbecker (12):
>>>        housekeeping: Move housekeeping related code to its own file
>>>        watchdog: Use housekeeping_cpumask() instead of ad-hoc version
>>>        housekeeping: Provide a dynamic off-case to housekeeping_any_cpu()
>>>        housekeeping: Make housekeeping cpumask private
>>>        housekeeping: Use its own static key
>>>        housekeeping: Rename is_housekeeping_cpu to housekeeping_cpu
>>>        housekeeping: Move it under its own config, independant from NO_HZ
>>>        housekeeping: Introduce housekeeping flags
>>>        housekeeping: Handle nohz_full= parameter
>>>        housekeeping: Move isolcpus to housekeeping
>>>        housekeeping: Add basic isolcpus flags
>>>        housekeeping: Document isolcpus flags
>>>
>>>
>>>   Documentation/admin-guide/kernel-parameters.txt |  33 +++---
>>>   drivers/base/cpu.c                              |  11 +-
>>>   drivers/net/ethernet/tile/tilegx.c              |   6 +-
>>>   include/linux/housekeeping.h                    |  51 ++++++++
>>>   include/linux/sched.h                           |   2 -
>>>   include/linux/tick.h                            |  39 +------
>>>   init/Kconfig                                    |   7 ++
>>>   init/main.c                                     |   2 +
>>>   kernel/Makefile                                 |   1 +
>>>   kernel/cgroup/cpuset.c                          |  15 +--
>>>   kernel/housekeeping.c                           | 149
>>> ++++++++++++++++++++++++
>>>   kernel/rcu/tree_plugin.h                        |   3 +-
>>>   kernel/rcu/update.c                             |   3 +-
>>>   kernel/sched/core.c                             |  25 +---
>>>   kernel/sched/fair.c                             |   3 +-
>>>   kernel/sched/topology.c                         |  24 +---
>>>   kernel/time/tick-sched.c                        |  31 +----
>>>   kernel/watchdog.c                               |  13 +--
>>>   18 files changed, 276 insertions(+), 142 deletions(-)
>>
>>
>> Yeah, so while I agree that all this functionality needs to be factored
>> out and organized, I have a problem with this specific high level
>> organization.
>>
>> The main problem I think is that it's all called "housekeeping", which is
>> pretty
>> fuzzy and opaque. What does 'housekeeping' exactly mean? A dozen of
>> details if you
>> look at the code - and this name does not make it much easier to think
>> about this
>> whole problem category.
>
>
> Indeed I feel that housekeeping is probably not the best concept to express
> all these things. I'm all for something clearer.
>
>>
>> So how about introducing _two_ new high level concepts:
>>
>>    1) 'global time handling'
>>    2) 'double async CPU callbacks'
>>
>> The notion of 'global time' handling is obvious to everyone I think: it
>> involves
>> the system-global guarantee that certain kernel jobs will be executed
>> periodically. At least one CPU in the system needs to handle 'global
>> time'.
>>
>> The notion of 'double async CPU callbacks' is less obvious: it involves
>> the action
>> of invoking a callback on a CPU, that might be executed on _another_ CPU.
>>
>> I.e. there are 3 CPUs involved:
>>
>>         - the invoking CPU
>>         - the target CPU
>>         - the CPU(s!) that will handle the callback (the housekeeping CPU
>> mask)
>>
>> For example the kmem-cache on_each_cpu() calls in mm/slab.c would fall
>> into this
>> category.
>
>
> Hmm, I'm not clear on this one. Do you mean works that can be executed
> concurrently?
>
>>
>> I don't know to what extent it makes sense to formalize and unify these
>> facilities: it's certain that the (former) housekeeping CPU mask should be
>> shared
>> by these two facilities: the CPU executing global time callbacks
>> periodically
>> should be one of the CPUs that execute double-async CPU callbacks.
>>
>> But by separating all this functionality into these two categories, it's
>> already
>> much easier to me to argue about which bit does what and why.
>
>
> Note that some housekeeping concepts may not fall into any of these
> categories. For example domain isolation.
>
> Thanks.

Hi Ingo,

Any detail to add about this housekeeping division?

Thanks!

Re: [GIT PULL] Introduce housekeeping subsystem v4

[Ingo Molnar]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> Indeed I feel that housekeeping is probably not the best concept to express
> all these things. I'm all for something clearer.
> 
> > 
> > So how about introducing _two_ new high level concepts:
> > 
> >    1) 'global time handling'
> >    2) 'double async CPU callbacks'
> > 
> > The notion of 'global time' handling is obvious to everyone I think: it involves
> > the system-global guarantee that certain kernel jobs will be executed
> > periodically. At least one CPU in the system needs to handle 'global time'.
> > 
> > The notion of 'double async CPU callbacks' is less obvious: it involves the action
> > of invoking a callback on a CPU, that might be executed on _another_ CPU.
> > 
> > I.e. there are 3 CPUs involved:
> > 
> > 	- the invoking CPU
> > 	- the target CPU
> > 	- the CPU(s!) that will handle the callback (the housekeeping CPU mask)
> > 
> > For example the kmem-cache on_each_cpu() calls in mm/slab.c would fall into this
> > category.
> 
> Hmm, I'm not clear on this one. Do you mean works that can be executed
> concurrently?

I mean code like:

 triton:~/tip> git grep on_each_cpu mm
 mm/page_alloc.c:         * cpu to drain that CPU pcps and on_each_cpu_mask
 mm/slab.c:      on_each_cpu(do_drain, cachep, 1);
 mm/slub.c:      on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1, GFP_ATOMIC);
 mm/vmstat.c:    err = schedule_on_each_cpu(refresh_vm_stats);

is something we want to execute on 'housekeeping CPUs' as well, to not disturb the 
isolated CPUs, right?

I.e. right now most (or all) of your patchset could be done using the 
'global_time_*()' (or so) naming - I just wanted to mention that work related to 
global timeline is not the only jobs that housekeeping CPUs will have to 
eventually execute.

> > I don't know to what extent it makes sense to formalize and unify these
> > facilities: it's certain that the (former) housekeeping CPU mask should be shared
> > by these two facilities: the CPU executing global time callbacks periodically
> > should be one of the CPUs that execute double-async CPU callbacks.
> > 
> > But by separating all this functionality into these two categories, it's already
> > much easier to me to argue about which bit does what and why.
> 
> Note that some housekeeping concepts may not fall into any of these
> categories. For example domain isolation.

Could you describe domain isolation?

Thanks,

	Ingo

Re: [GIT PULL] Introduce housekeeping subsystem v4

[Frederic Weisbecker]

2017-10-20 10:17 UTC+02:00, Ingo Molnar <mingo@kernel.org>:
> I mean code like:
>
>  triton:~/tip> git grep on_each_cpu mm
>  mm/page_alloc.c:         * cpu to drain that CPU pcps and on_each_cpu_mask
>  mm/slab.c:      on_each_cpu(do_drain, cachep, 1);
>  mm/slub.c:      on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1,
> GFP_ATOMIC);
>  mm/vmstat.c:    err = schedule_on_each_cpu(refresh_vm_stats);
>
> is something we want to execute on 'housekeeping CPUs' as well, to not
> disturb the
> isolated CPUs, right?

I see, so indeed that's the kind of thing we want to also confine to
housekeeping as
well whenever possible but these cases require special treatment that need to be
handled by the subsystem in charge. For example vmstat has the vmstat_sheperd
thing which allows to drive those timers adaptively on demand to make sure that
userspace isn't interrupted. The others will likely need some similar treatment.

For now I only see vmstat having such a feature and it acts
transparently. There is
also the LRU flush (IIRC) which needs to be called for example before
returning to
userspace to avoid IPIs. Such things may indeed need special treatment. With the
current patchset it could be a housekeeping flag.

>
> I.e. right now most (or all) of your patchset could be done using the
> 'global_time_*()' (or so) naming - I just wanted to mention that work
> related to
> global timeline is not the only jobs that housekeeping CPUs will have to
> eventually execute.

I'd rather talk about CPU affinity than global time. For example
timers, watchdog, idle load balancing are about periodic events but
workqueues (not the deffered ones), domain isolation (isolcpus), NAPI
polling are perhaps more event driven.

But indeed global timeline based periodic events are not all of what
housekeeping needs to care about.

>
>> > I don't know to what extent it makes sense to formalize and unify these
>> > facilities: it's certain that the (former) housekeeping CPU mask should
>> > be shared
>> > by these two facilities: the CPU executing global time callbacks
>> > periodically
>> > should be one of the CPUs that execute double-async CPU callbacks.
>> >
>> > But by separating all this functionality into these two categories, it's
>> > already
>> > much easier to me to argue about which bit does what and why.
>>
>> Note that some housekeeping concepts may not fall into any of these
>> categories. For example domain isolation.
>
> Could you describe domain isolation?

This is the isolcpus thing which excludes a set of CPUs from the whole
domain tree. That one
doesn't fall into any category we talked about.

In fact, CPU affinity is the only high level concept I found to gather
all these housekeeping
elements.

Perhaps I should use "cpu_isolation" instead of "housekeeping" naming.

Thanks.

Re: [GIT PULL] Introduce housekeeping subsystem v4

[Chris Metcalf]

On 10/20/2017 10:29 AM, Frederic Weisbecker wrote:
> 2017-10-20 10:17 UTC+02:00, Ingo Molnar <mingo@kernel.org>:
>> I mean code like:
>>
>>   triton:~/tip> git grep on_each_cpu mm
>>   mm/page_alloc.c:         * cpu to drain that CPU pcps and on_each_cpu_mask
>>   mm/slab.c:      on_each_cpu(do_drain, cachep, 1);
>>   mm/slub.c:      on_each_cpu_cond(has_cpu_slab, flush_cpu_slab, s, 1,
>> GFP_ATOMIC);
>>   mm/vmstat.c:    err = schedule_on_each_cpu(refresh_vm_stats);
>>
>> is something we want to execute on 'housekeeping CPUs' as well, to not
>> disturb the
>> isolated CPUs, right?
> I see, so indeed that's the kind of thing we want to also confine to
> housekeeping as
> well whenever possible but these cases require special treatment that need to be
> handled by the subsystem in charge. For example vmstat has the vmstat_sheperd
> thing which allows to drive those timers adaptively on demand to make sure that
> userspace isn't interrupted. The others will likely need some similar treatment.
>
> For now I only see vmstat having such a feature and it acts
> transparently. There is
> also the LRU flush (IIRC) which needs to be called for example before
> returning to
> userspace to avoid IPIs. Such things may indeed need special treatment. With the
> current patchset it could be a housekeeping flag.

I have been working to update the task isolation support the last few
days and though it's not quite ready to post (probably will be Monday
or Tuesday), I have sorted out those issues from task isolation's
perspective.  It turns out that you can both quiesce the
vmstat_shepherd, as well as drain the LRU per-cpu pages, while
interrupts are disabled on the way back to userspace.

Whether shifting this work to housekeeping cores at all times makes
sense seems like a much more open question.  The idea of task
isolation is to provide a harder guarantee of isolation, and in
particular to shift work to the moment that you return to userspace,
rather than allowing it to happen later.  It does seem likely that
there are some things you'd want to do on the core itself most of the
time, and just suppress for true task isolation if requested, rather
than trying to move them to the housekeeping cores.

But, it's certainly worth looking at both options and seeing how it
plays out.  The less complicated the task isolation return-to-user
path is, the better.  (The idea of task isolation seems like a win no
matter what, to allow ensuring kernel isolation when you absolutely
require it.)

The current task isolation tree is in the "dataplane" branch at
git://git.kernel.org/pub/scm/linux/kernel/git/cmetcalf/linux-tile.git

-- 
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com

Re: [GIT PULL] Introduce housekeeping subsystem v4

[Ingo Molnar]

* Frederic Weisbecker <frederic@kernel.org> wrote:

> In fact, CPU affinity is the only high level concept I found to gather all these 
> housekeeping elements.
> 
> Perhaps I should use "cpu_isolation" instead of "housekeeping" naming.

The problem with names based on that, like cpu_isolation_map, is that there's 
really two concepts here: there's the isolcpus feature where the 'mask' is in fact 
the CPUs that are isolated - while the 'housekeeping CPUs' is the mask of CPUs 
that _support_ the isolated set of CPUs. The two are different roles but easily 
confused if named similarly.

So I guess 'housekeeping CPUs' is as good as it gets for now.

Mind sending a refreshed queue against the latest kernel? There's some new 
conflicts in kernel/watchdog.c for example.

Thanks,

	Ingo

Re: [GIT PULL] Introduce housekeeping subsystem v4

[Frederic Weisbecker]

2017-10-23 14:06 UTC+02:00, Ingo Molnar <mingo@kernel.org>:
>
> * Frederic Weisbecker <frederic@kernel.org> wrote:
>
>> In fact, CPU affinity is the only high level concept I found to gather all
>> these
>> housekeeping elements.
>>
>> Perhaps I should use "cpu_isolation" instead of "housekeeping" naming.
>
> The problem with names based on that, like cpu_isolation_map, is that
> there's
> really two concepts here: there's the isolcpus feature where the 'mask' is
> in fact
> the CPUs that are isolated - while the 'housekeeping CPUs' is the mask of
> CPUs
> that _support_ the isolated set of CPUs. The two are different roles but
> easily
> confused if named similarly.

Indeed, housekeeping is in fact the machinery that supports cpu isolation.

> So I guess 'housekeeping CPUs' is as good as it gets for now.

Agreed, And I have no doubt the concept will evolve. We can always
split it into high level concepts such as those we discussed if it
appears necessary later.

> Mind sending a refreshed queue against the latest kernel? There's some new
> conflicts in kernel/watchdog.c for example.

Sure, here is a rebase against -rc6:

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
    core/isolation-v5

Thanks!