[PATCH 0/3] fix rescaling of scheduler tunabled

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* [PATCH 0/3] fix rescaling of scheduler tunabled
@ 2009-11-27 14:45 ehrhardt
  2009-11-27 14:45 ` [PATCH 1/3] sched: fix missing sched tunable recalculation on cpu add/remove ehrhardt
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: ehrhardt @ 2009-11-27 14:45 UTC (permalink / raw)
  To: peterz, mingo, linux-kernel; +Cc: ehrhardt, Holger.Wolf, epasch, schwidefsky

This patch series is based on the ideas of Peter Zijlstra and me in the
discussion how to fix missing updates to the scheduler tunables in case
of cpu hot add/remove. The values are scaled on boot time but not (yet)
in the runtime #cpu changes.

The series has not yet got the testing it shouldhave, just some basic
functionality tests. But working day is ending and the patches are fine
enough for another round of discussion about the basic ideas and
implementation.

Series contains:
[PATCH 1/3] sched: fix missing sched tunable recalculation on cpu add/remove
[PATCH 2/3] sched: make tunable scaling style configurable
[PATCH 3/3] sched: update normalized values on user updates via proc

[diffstat]
 kernel/sched.c                                  |   41 ++++++++++++++----------
 kernel/sched_fair.c                             |   27 +++++++++++++++
 kernel/sysctl.c                                 |   12 ++++---
 linux-2.6-git-schedrecalc/include/linux/sched.h |   11 +++++-
 linux-2.6-git-schedrecalc/kernel/sched.c        |   15 ++++++++
 linux-2.6-git-schedrecalc/kernel/sched_debug.c  |   10 +++++
 linux-2.6-git-schedrecalc/kernel/sched_fair.c   |   12 +++++++
 linux-2.6-git-schedrecalc/kernel/sysctl.c       |   14 ++++++++
 8 files changed, 120 insertions(+), 22 deletions(-)

^ permalink raw reply	[flat|nested] 4+ messages in thread

* [PATCH 1/3] sched: fix missing sched tunable recalculation on cpu add/remove
  2009-11-27 14:45 [PATCH 0/3] fix rescaling of scheduler tunabled ehrhardt
@ 2009-11-27 14:45 ` ehrhardt
  2009-11-27 14:45 ` [PATCH 2/3] sched: make tunable scaling style configurable ehrhardt
  2009-11-27 14:45 ` [PATCH 3/3] sched: update normalized values on user updates via proc ehrhardt
  2 siblings, 0 replies; 4+ messages in thread
From: ehrhardt @ 2009-11-27 14:45 UTC (permalink / raw)
  To: peterz, mingo, linux-kernel; +Cc: ehrhardt, Holger.Wolf, epasch, schwidefsky

From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

Based on Peter Zijlstras patch suggestion this enables recalculation of the
scheduler tunables in response of a change in the number of cpus.
It also adds a max of eight cpus that are considered in that scaling.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
---

[diffstat]
 sched.c      |   29 ++++++++++++++++-------------
 sched_fair.c |   16 ++++++++++++++++
 2 files changed, 32 insertions(+), 13 deletions(-)

[diff]
Index: linux-2.6-git-schedrecalc/kernel/sched.c
===================================================================
--- linux-2.6-git-schedrecalc.orig/kernel/sched.c
+++ linux-2.6-git-schedrecalc/kernel/sched.c
@@ -814,6 +814,7 @@ const_debug unsigned int sysctl_sched_nr
  * default: 0.25ms
  */
 unsigned int sysctl_sched_shares_ratelimit = 250000;
+unsigned int normalized_sysctl_sched_shares_ratelimit = 250000;
 
 /*
  * Inject some fuzzyness into changing the per-cpu group shares
@@ -1810,6 +1811,7 @@ static void cfs_rq_set_shares(struct cfs
 #endif
 
 static void calc_load_account_active(struct rq *this_rq);
+static void update_sysctl(void);
 
 #include "sched_stats.h"
 #include "sched_idletask.c"
@@ -7003,22 +7005,23 @@ cpumask_var_t nohz_cpu_mask;
  *
  * This idea comes from the SD scheduler of Con Kolivas:
  */
-static inline void sched_init_granularity(void)
+static void update_sysctl(void)
 {
-	unsigned int factor = 1 + ilog2(num_online_cpus());
-	const unsigned long limit = 200000000;
-
-	sysctl_sched_min_granularity *= factor;
-	if (sysctl_sched_min_granularity > limit)
-		sysctl_sched_min_granularity = limit;
-
-	sysctl_sched_latency *= factor;
-	if (sysctl_sched_latency > limit)
-		sysctl_sched_latency = limit;
+	unsigned int cpus = max(num_online_cpus(), 8U);
+	unsigned int factor = 1 + ilog2(cpus);
 
-	sysctl_sched_wakeup_granularity *= factor;
+#define SET_SYSCTL(name) \
+	sysctl_##name = (factor) * normalized_sysctl_##name
+	SET_SYSCTL(sched_min_granularity);
+	SET_SYSCTL(sched_latency);
+	SET_SYSCTL(sched_wakeup_granularity);
+	SET_SYSCTL(sched_shares_ratelimit);
+#undef SET_SYSCTL
+}
 
-	sysctl_sched_shares_ratelimit *= factor;
+static inline void sched_init_granularity(void)
+{
+	update_sysctl();
 }
 
 #ifdef CONFIG_SMP
Index: linux-2.6-git-schedrecalc/kernel/sched_fair.c
===================================================================
--- linux-2.6-git-schedrecalc.orig/kernel/sched_fair.c
+++ linux-2.6-git-schedrecalc/kernel/sched_fair.c
@@ -35,12 +35,14 @@
  *  run vmstat and monitor the context-switches (cs) field)
  */
 unsigned int sysctl_sched_latency = 5000000ULL;
+unsigned int normalized_sysctl_sched_latency = 5000000ULL;
 
 /*
  * Minimal preemption granularity for CPU-bound tasks:
  * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
  */
 unsigned int sysctl_sched_min_granularity = 1000000ULL;
+unsigned int normalized_sysctl_sched_min_granularity = 1000000ULL;
 
 /*
  * is kept at sysctl_sched_latency / sysctl_sched_min_granularity
@@ -70,6 +72,7 @@ unsigned int __read_mostly sysctl_sched_
  * have immediate wakeup/sleep latencies.
  */
 unsigned int sysctl_sched_wakeup_granularity = 1000000UL;
+unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
 
 const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
 
@@ -1850,6 +1853,17 @@ move_one_task_fair(struct rq *this_rq, i
 
 	return 0;
 }
+
+static void rq_online_fair(struct rq *rq)
+{
+	update_sysctl();
+}
+
+static void rq_offline_fair(struct rq *rq)
+{
+	update_sysctl();
+}
+
 #endif /* CONFIG_SMP */
 
 /*
@@ -1997,6 +2011,8 @@ static const struct sched_class fair_sch
 
 	.load_balance		= load_balance_fair,
 	.move_one_task		= move_one_task_fair,
+	.rq_online		= rq_online_fair,
+	.rq_offline		= rq_offline_fair,
 #endif
 
 	.set_curr_task          = set_curr_task_fair,

^ permalink raw reply	[flat|nested] 4+ messages in thread

* [PATCH 2/3] sched: make tunable scaling style configurable
  2009-11-27 14:45 [PATCH 0/3] fix rescaling of scheduler tunabled ehrhardt
  2009-11-27 14:45 ` [PATCH 1/3] sched: fix missing sched tunable recalculation on cpu add/remove ehrhardt
@ 2009-11-27 14:45 ` ehrhardt
  2009-11-27 14:45 ` [PATCH 3/3] sched: update normalized values on user updates via proc ehrhardt
  2 siblings, 0 replies; 4+ messages in thread
From: ehrhardt @ 2009-11-27 14:45 UTC (permalink / raw)
  To: peterz, mingo, linux-kernel; +Cc: ehrhardt, Holger.Wolf, epasch, schwidefsky

From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

As scaling now takes place on all kind of cpu add/remove events a user that
configures values via proc should be able to configure if his set values are
still rescaled or kept whatever happens.

As the comments state that log2 was just a second guess that worked the
interface is not just designed for on/off, but to choose a scaling type.
Currently this allows none, log and linear, but more important it allwos us
to keep the interface even if someone has an even better idea how to scale
the values.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
---

[diffstat]
 include/linux/sched.h |   11 ++++++++++-
 kernel/sched.c        |   15 +++++++++++++++
 kernel/sched_debug.c  |   10 ++++++++++
 kernel/sched_fair.c   |   12 ++++++++++++
 kernel/sysctl.c       |   14 ++++++++++++++
 5 files changed, 61 insertions(+), 1 deletion(-)

[diff]
Index: linux-2.6-git-schedrecalc/include/linux/sched.h
===================================================================
--- linux-2.6-git-schedrecalc.orig/include/linux/sched.h
+++ linux-2.6-git-schedrecalc/include/linux/sched.h
@@ -1899,6 +1899,15 @@ extern unsigned int sysctl_sched_wakeup_
 extern unsigned int sysctl_sched_shares_ratelimit;
 extern unsigned int sysctl_sched_shares_thresh;
 extern unsigned int sysctl_sched_child_runs_first;
+
+enum sched_tunable_scaling
+{
+	SCHED_TUNABLESCALING_NONE,
+	SCHED_TUNABLESCALING_LOG,
+	SCHED_TUNABLESCALING_LINEAR,
+	SCHED_TUNABLESCALING_END,
+};
+extern enum sched_tunable_scaling sysctl_sched_tunable_scaling;
 #ifdef CONFIG_SCHED_DEBUG
 extern unsigned int sysctl_sched_features;
 extern unsigned int sysctl_sched_migration_cost;
@@ -1906,7 +1915,7 @@ extern unsigned int sysctl_sched_nr_migr
 extern unsigned int sysctl_sched_time_avg;
 extern unsigned int sysctl_timer_migration;
 
-int sched_nr_latency_handler(struct ctl_table *table, int write,
+int sched_proc_update_handler(struct ctl_table *table, int write,
 		void __user *buffer, size_t *length,
 		loff_t *ppos);
 #endif
Index: linux-2.6-git-schedrecalc/kernel/sched.c
===================================================================
--- linux-2.6-git-schedrecalc.orig/kernel/sched.c
+++ linux-2.6-git-schedrecalc/kernel/sched.c
@@ -7010,6 +7010,21 @@ static void update_sysctl(void)
 	unsigned int cpus = max(num_online_cpus(), 8U);
 	unsigned int factor = 1 + ilog2(cpus);
 
+	unsigned int factor;
+
+	switch (sysctl_sched_tunable_scaling) {
+		case SCHED_TUNABLESCALING_NONE:
+			factor = 1;
+			break;
+		case SCHED_TUNABLESCALING_LINEAR:
+			factor = cpus;
+			break;
+		case SCHED_TUNABLESCALING_LOG:
+		default:
+			factor = 1 + ilog2(cpus);
+			break;
+	}
+
 #define SET_SYSCTL(name) \
 	sysctl_##name = (factor) * normalized_sysctl_##name
 	SET_SYSCTL(sched_min_granularity);
Index: linux-2.6-git-schedrecalc/kernel/sched_fair.c
===================================================================
--- linux-2.6-git-schedrecalc.orig/kernel/sched_fair.c
+++ linux-2.6-git-schedrecalc/kernel/sched_fair.c
@@ -21,6 +21,7 @@
  */
 
 #include <linux/latencytop.h>
+#include <linux/sched.h>
 
 /*
  * Targeted preemption latency for CPU-bound tasks:
@@ -38,6 +39,17 @@ unsigned int sysctl_sched_latency = 5000
 unsigned int normalized_sysctl_sched_latency = 5000000ULL;
 
 /*
+ * The initial- and re-scaling of tunables is configurable
+ * (default SCHED_TUNABLESCALING_LOG = *(1+ilog(ncpus))
+ *
+ * Options are:
+ * SCHED_TUNABLESCALING_NONE - unscaled, always *1
+ * SCHED_TUNABLESCALING_LOG - scaled logarithmical, *1+ilog(ncpus)
+ * SCHED_TUNABLESCALING_LINEAR - scaled linear, *ncpus
+ */
+enum sched_tunable_scaling sysctl_sched_tunable_scaling = SCHED_TUNABLESCALING_LOG;
+
+/*
  * Minimal preemption granularity for CPU-bound tasks:
  * (default: 1 msec * (1 + ilog(ncpus)), units: nanoseconds)
  */
Index: linux-2.6-git-schedrecalc/kernel/sysctl.c
===================================================================
--- linux-2.6-git-schedrecalc.orig/kernel/sysctl.c
+++ linux-2.6-git-schedrecalc/kernel/sysctl.c
@@ -248,6 +248,8 @@ static int min_sched_granularity_ns = 10
 static int max_sched_granularity_ns = NSEC_PER_SEC;	/* 1 second */
 static int min_wakeup_granularity_ns;			/* 0 usecs */
 static int max_wakeup_granularity_ns = NSEC_PER_SEC;	/* 1 second */
+static int min_sched_tunable_scaling = SCHED_TUNABLESCALING_NONE;
+static int max_sched_tunable_scaling = SCHED_TUNABLESCALING_END-1;
 #endif
 
 static struct ctl_table kern_table[] = {
@@ -303,6 +305,18 @@ static struct ctl_table kern_table[] = {
 	},
 	{
 		.ctl_name	= CTL_UNNUMBERED,
+		.procname	= "sched_tunable_scaling",
+		.data		= &sysctl_sched_tunable_scaling,
+		.maxlen		= sizeof(enum sched_tunable_scaling),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec_minmax,
+		.strategy	= &sysctl_intvec,
+		.extra1		= &min_sched_tunable_scaling,
+		.extra2		= &max_sched_tunable_scaling,
+	},
+
+	{
+		.ctl_name	= CTL_UNNUMBERED,
 		.procname	= "sched_shares_thresh",
 		.data		= &sysctl_sched_shares_thresh,
 		.maxlen		= sizeof(unsigned int),
Index: linux-2.6-git-schedrecalc/kernel/sched_debug.c
===================================================================
--- linux-2.6-git-schedrecalc.orig/kernel/sched_debug.c
+++ linux-2.6-git-schedrecalc/kernel/sched_debug.c
@@ -305,6 +305,12 @@ static void print_cpu(struct seq_file *m
 	print_rq(m, rq, cpu);
 }
 
+static const char *sched_tunable_scaling_names[] = {
+	"none",
+	"logaritmic",
+	"linear"
+};
+
 static int sched_debug_show(struct seq_file *m, void *v)
 {
 	u64 now = ktime_to_ns(ktime_get());
@@ -330,6 +336,10 @@ static int sched_debug_show(struct seq_f
 #undef PN
 #undef P
 
+	SEQ_printf(m, "  .%-40s: %d (%s)\n", "sysctl_sched_tunable_scaling",
+		sysctl_sched_tunable_scaling,
+		sched_tunable_scaling_names[sysctl_sched_tunable_scaling]);
+
 	for_each_online_cpu(cpu)
 		print_cpu(m, cpu);
 

^ permalink raw reply	[flat|nested] 4+ messages in thread

* [PATCH 3/3] sched: update normalized values on user updates via proc
  2009-11-27 14:45 [PATCH 0/3] fix rescaling of scheduler tunabled ehrhardt
  2009-11-27 14:45 ` [PATCH 1/3] sched: fix missing sched tunable recalculation on cpu add/remove ehrhardt
  2009-11-27 14:45 ` [PATCH 2/3] sched: make tunable scaling style configurable ehrhardt
@ 2009-11-27 14:45 ` ehrhardt
  2 siblings, 0 replies; 4+ messages in thread
From: ehrhardt @ 2009-11-27 14:45 UTC (permalink / raw)
  To: peterz, mingo, linux-kernel; +Cc: ehrhardt, Holger.Wolf, epasch, schwidefsky

From: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>

This patch updates the internally used scheduler tuning values that are
normalized to one cpu in case a user sets new values via sysfs.

Together with patch 2 of this series this allows to let user configured
values scale (or not) to cpu add/remove events taking place later.

Signed-off-by: Christian Ehrhardt <ehrhardt@linux.vnet.ibm.com>
---

[diffstat]
 sched.c      |   12 +++++++++---
 sched_fair.c |   11 ++++++++++-
 sysctl.c     |   12 ++++++++----
 3 files changed, 27 insertions(+), 8 deletions(-)

[diff]
Index: linux-2.6-git-schedrecalc/kernel/sched.c
===================================================================
--- linux-2.6-git-schedrecalc.orig/kernel/sched.c
+++ linux-2.6-git-schedrecalc/kernel/sched.c
@@ -1812,6 +1812,7 @@ static void cfs_rq_set_shares(struct cfs
 
 static void calc_load_account_active(struct rq *this_rq);
 static void update_sysctl(void);
+static int get_update_sysctl_factor(void);
 
 #include "sched_stats.h"
 #include "sched_idletask.c"
@@ -7005,11 +7006,9 @@ cpumask_var_t nohz_cpu_mask;
  *
  * This idea comes from the SD scheduler of Con Kolivas:
  */
-static void update_sysctl(void)
+static int get_update_sysctl_factor(void)
 {
 	unsigned int cpus = max(num_online_cpus(), 8U);
-	unsigned int factor = 1 + ilog2(cpus);
-
 	unsigned int factor;
 
 	switch (sysctl_sched_tunable_scaling) {
@@ -7025,6 +7024,13 @@ static void update_sysctl(void)
 			break;
 	}
 
+	return factor;
+}
+
+static void update_sysctl(void)
+{
+	unsigned int factor = get_update_sysctl_factor();
+
 #define SET_SYSCTL(name) \
 	sysctl_##name = (factor) * normalized_sysctl_##name
 	SET_SYSCTL(sched_min_granularity);
Index: linux-2.6-git-schedrecalc/kernel/sched_fair.c
===================================================================
--- linux-2.6-git-schedrecalc.orig/kernel/sched_fair.c
+++ linux-2.6-git-schedrecalc/kernel/sched_fair.c
@@ -398,11 +398,12 @@ static struct sched_entity *__pick_last_
  */
 
 #ifdef CONFIG_SCHED_DEBUG
-int sched_nr_latency_handler(struct ctl_table *table, int write,
+int sched_proc_update_handler(struct ctl_table *table, int write,
 		void __user *buffer, size_t *lenp,
 		loff_t *ppos)
 {
 	int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+	int factor = get_update_sysctl_factor();
 
 	if (ret || !write)
 		return ret;
@@ -410,6 +411,14 @@ int sched_nr_latency_handler(struct ctl_
 	sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
 					sysctl_sched_min_granularity);
 
+#define WRT_SYSCTL(name) \
+	normalized_sysctl_##name = sysctl_##name / (factor)
+	WRT_SYSCTL(sched_min_granularity);
+	WRT_SYSCTL(sched_latency);
+	WRT_SYSCTL(sched_wakeup_granularity);
+	WRT_SYSCTL(sched_shares_ratelimit);
+#undef WRT_SYSCTL
+
 	return 0;
 }
 #endif
Index: linux-2.6-git-schedrecalc/kernel/sysctl.c
===================================================================
--- linux-2.6-git-schedrecalc.orig/kernel/sysctl.c
+++ linux-2.6-git-schedrecalc/kernel/sysctl.c
@@ -250,6 +250,8 @@ static int min_wakeup_granularity_ns;
 static int max_wakeup_granularity_ns = NSEC_PER_SEC;	/* 1 second */
 static int min_sched_tunable_scaling = SCHED_TUNABLESCALING_NONE;
 static int max_sched_tunable_scaling = SCHED_TUNABLESCALING_END-1;
+static int min_sched_shares_ratelimit = 100000; /* 100 usec */
+static int max_sched_shares_ratelimit = NSEC_PER_SEC; /* 1 second */
 #endif
 
 static struct ctl_table kern_table[] = {
@@ -268,7 +270,7 @@ static struct ctl_table kern_table[] = {
 		.data		= &sysctl_sched_min_granularity,
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
-		.proc_handler	= &sched_nr_latency_handler,
+		.proc_handler	= &sched_proc_update_handler,
 		.strategy	= &sysctl_intvec,
 		.extra1		= &min_sched_granularity_ns,
 		.extra2		= &max_sched_granularity_ns,
@@ -279,7 +281,7 @@ static struct ctl_table kern_table[] = {
 		.data		= &sysctl_sched_latency,
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
-		.proc_handler	= &sched_nr_latency_handler,
+		.proc_handler	= &sched_proc_update_handler,
 		.strategy	= &sysctl_intvec,
 		.extra1		= &min_sched_granularity_ns,
 		.extra2		= &max_sched_granularity_ns,
@@ -290,7 +292,7 @@ static struct ctl_table kern_table[] = {
 		.data		= &sysctl_sched_wakeup_granularity,
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
-		.proc_handler	= &proc_dointvec_minmax,
+		.proc_handler	= &sched_proc_update_handler,
 		.strategy	= &sysctl_intvec,
 		.extra1		= &min_wakeup_granularity_ns,
 		.extra2		= &max_wakeup_granularity_ns,
@@ -301,7 +303,9 @@ static struct ctl_table kern_table[] = {
 		.data		= &sysctl_sched_shares_ratelimit,
 		.maxlen		= sizeof(unsigned int),
 		.mode		= 0644,
-		.proc_handler	= &proc_dointvec,
+		.proc_handler	= &sched_proc_update_handler,
+		.extra1		= &min_sched_shares_ratelimit,
+		.extra2		= &max_sched_shares_ratelimit,
 	},
 	{
 		.ctl_name	= CTL_UNNUMBERED,

^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2009-11-27 14:46 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2009-11-27 14:45 [PATCH 0/3] fix rescaling of scheduler tunabled ehrhardt
2009-11-27 14:45 ` [PATCH 1/3] sched: fix missing sched tunable recalculation on cpu add/remove ehrhardt
2009-11-27 14:45 ` [PATCH 2/3] sched: make tunable scaling style configurable ehrhardt
2009-11-27 14:45 ` [PATCH 3/3] sched: update normalized values on user updates via proc ehrhardt

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