From: Valentin Schneider <valentin.schneider@arm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, peterz@infradead.org,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com
Subject: [PATCH v3 9/9] sched/topology: Define and use shortcut pointers for wakeup sd_flag scan
Date: Wed, 15 Apr 2020 22:05:12 +0100 [thread overview]
Message-ID: <20200415210512.805-10-valentin.schneider@arm.com> (raw)
In-Reply-To: <20200415210512.805-1-valentin.schneider@arm.com>
Reworking select_task_rq_fair()'s domain walk exposed that !want_affine
wakeups only look for highest sched_domain with the required sd_flag
set. This is something we can cache at sched domain build time to slightly
optimize select_task_rq_fair(). Note that this isn't a "free" optimization:
it costs us 3 pointers per CPU.
Add cached per-CPU pointers for the highest domains with SD_BALANCE_WAKE,
SD_BALANCE_EXEC and SD_BALANCE_FORK. Use them in select_task_rq_fair().
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
kernel/sched/fair.c | 25 +++++++++++++------------
kernel/sched/sched.h | 3 +++
kernel/sched/topology.c | 12 ++++++++++++
3 files changed, 28 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6f8cdb99f4a0..db4fb29a88d9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6631,17 +6631,6 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
int want_affine = 0;
int sd_flag;
- switch (wake_flags & (WF_TTWU | WF_FORK | WF_EXEC)) {
- case WF_TTWU:
- sd_flag = SD_BALANCE_WAKE;
- break;
- case WF_FORK:
- sd_flag = SD_BALANCE_FORK;
- break;
- default:
- sd_flag = SD_BALANCE_EXEC;
- }
-
if (wake_flags & WF_TTWU) {
record_wakee(p);
@@ -6657,7 +6646,19 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
rcu_read_lock();
- sd = highest_flag_domain(cpu, sd_flag);
+ switch (wake_flags & (WF_TTWU | WF_FORK | WF_EXEC)) {
+ case WF_TTWU:
+ sd_flag = SD_BALANCE_WAKE;
+ sd = rcu_dereference(per_cpu(sd_balance_wake, cpu));
+ break;
+ case WF_FORK:
+ sd_flag = SD_BALANCE_FORK;
+ sd = rcu_dereference(per_cpu(sd_balance_fork, cpu));
+ break;
+ default:
+ sd_flag = SD_BALANCE_EXEC;
+ sd = rcu_dereference(per_cpu(sd_balance_exec, cpu));
+ }
/*
* If !want_affine, we just look for the highest domain where
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 448f5d630544..4b014103affb 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1423,6 +1423,9 @@ DECLARE_PER_CPU(int, sd_llc_size);
DECLARE_PER_CPU(int, sd_llc_id);
DECLARE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared);
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_numa);
+DECLARE_PER_CPU(struct sched_domain __rcu *, sd_balance_wake);
+DECLARE_PER_CPU(struct sched_domain __rcu *, sd_balance_fork);
+DECLARE_PER_CPU(struct sched_domain __rcu *, sd_balance_exec);
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
extern struct static_key_false sched_asym_cpucapacity;
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 1d7b446fac7d..66763c539bbd 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -618,6 +618,9 @@ DEFINE_PER_CPU(int, sd_llc_size);
DEFINE_PER_CPU(int, sd_llc_id);
DEFINE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared);
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_numa);
+DEFINE_PER_CPU(struct sched_domain __rcu *, sd_balance_wake);
+DEFINE_PER_CPU(struct sched_domain __rcu *, sd_balance_fork);
+DEFINE_PER_CPU(struct sched_domain __rcu *, sd_balance_exec);
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing);
DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity);
DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity);
@@ -644,6 +647,15 @@ static void update_top_cache_domain(int cpu)
sd = lowest_flag_domain(cpu, SD_NUMA);
rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
+ sd = highest_flag_domain(cpu, SD_BALANCE_WAKE);
+ rcu_assign_pointer(per_cpu(sd_balance_wake, cpu), sd);
+
+ sd = highest_flag_domain(cpu, SD_BALANCE_FORK);
+ rcu_assign_pointer(per_cpu(sd_balance_fork, cpu), sd);
+
+ sd = highest_flag_domain(cpu, SD_BALANCE_EXEC);
+ rcu_assign_pointer(per_cpu(sd_balance_exec, cpu), sd);
+
sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
rcu_assign_pointer(per_cpu(sd_asym_packing, cpu), sd);
--
2.24.0
next prev parent reply other threads:[~2020-04-15 21:07 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-15 21:05 [PATCH v3 0/9] sched: Streamline select_task_rq() & select_task_rq_fair() Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 1/9] sched/fair: find_idlest_group(): Remove unused sd_flag parameter Valentin Schneider
2020-04-16 7:40 ` Vincent Guittot
2020-05-01 18:22 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 2/9] sched/debug: Make sd->flags sysctl read-only Valentin Schneider
2020-05-01 18:22 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 3/9] sched: Remove checks against SD_LOAD_BALANCE Valentin Schneider
2020-05-01 18:22 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 4/9] sched/topology: Kill SD_LOAD_BALANCE Valentin Schneider
2020-05-01 18:22 ` [tip: sched/core] " tip-bot2 for Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 5/9] sched: Add WF_TTWU, WF_EXEC wakeup flags Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 6/9] sched: Kill select_task_rq()'s sd_flag parameter Valentin Schneider
2020-04-16 7:42 ` Vincent Guittot
2020-04-16 10:24 ` Valentin Schneider
2020-04-16 10:47 ` Peter Zijlstra
2020-04-16 11:43 ` Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 7/9] sched/fair: Dissociate wakeup decisions from SD flag value Valentin Schneider
2020-04-15 21:05 ` [PATCH v3 8/9] sched/fair: Split select_task_rq_fair want_affine logic Valentin Schneider
2020-04-15 21:05 ` Valentin Schneider [this message]
2020-04-16 7:46 ` [PATCH v3 9/9] sched/topology: Define and use shortcut pointers for wakeup sd_flag scan Vincent Guittot
2020-04-16 10:24 ` Valentin Schneider
2020-04-16 13:04 ` Dietmar Eggemann
2020-04-16 13:36 ` Vincent Guittot
2020-04-16 15:27 ` Valentin Schneider
2020-04-16 15:58 ` Vincent Guittot
2020-04-16 20:54 ` Valentin Schneider
2020-04-16 10:58 ` [PATCH v3 0/9] sched: Streamline select_task_rq() & select_task_rq_fair() Peter Zijlstra
2020-04-16 11:00 ` Peter Zijlstra
2020-04-16 11:02 ` Valentin Schneider
2020-04-16 13:00 ` Vincent Guittot
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