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Date: Tue, 6 Dec 2011 01:50:24 -0800
From: tip-bot for Mike Galbraith <mgalbraith@...e.de>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, mgalbraith@...e.de, hpa@...or.com,
mingo@...hat.com, a.p.zijlstra@...llo.nl, efault@....de,
tglx@...utronix.de, mingo@...e.hu
Subject: [tip:sched/core] sched: Use rt.nr_cpus_allowed to recover select_task_rq() cycles
Commit-ID: 76854c7e8f3f4172fef091e78d88b3b751463ac6
Gitweb: http://git.kernel.org/tip/76854c7e8f3f4172fef091e78d88b3b751463ac6
Author: Mike Galbraith <mgalbraith@...e.de>
AuthorDate: Tue, 22 Nov 2011 15:18:24 +0100
Committer: Ingo Molnar <mingo@...e.hu>
CommitDate: Tue, 6 Dec 2011 08:51:26 +0100
sched: Use rt.nr_cpus_allowed to recover select_task_rq() cycles
rt.nr_cpus_allowed is always available, use it to bail from select_task_rq()
when only one cpu can be used, and saves some cycles for pinned tasks.
See the line marked with '*' below:
# taskset -c 3 pipe-test
PerfTop: 997 irqs/sec kernel:89.5% exact: 0.0% [1000Hz cycles], (all, CPU: 3)
------------------------------------------------------------------------------------------------
Virgin Patched
samples pcnt function samples pcnt function
_______ _____ ___________________________ _______ _____ ___________________________
2880.00 10.2% __schedule 3136.00 11.3% __schedule
1634.00 5.8% pipe_read 1615.00 5.8% pipe_read
1458.00 5.2% system_call 1534.00 5.5% system_call
1382.00 4.9% _raw_spin_lock_irqsave 1412.00 5.1% _raw_spin_lock_irqsave
1202.00 4.3% pipe_write 1255.00 4.5% copy_user_generic_string
1164.00 4.1% copy_user_generic_string 1241.00 4.5% __switch_to
1097.00 3.9% __switch_to 929.00 3.3% mutex_lock
872.00 3.1% mutex_lock 846.00 3.0% mutex_unlock
687.00 2.4% mutex_unlock 804.00 2.9% pipe_write
682.00 2.4% native_sched_clock 713.00 2.6% native_sched_clock
643.00 2.3% system_call_after_swapgs 653.00 2.3% _raw_spin_unlock_irqrestore
617.00 2.2% sched_clock_local 633.00 2.3% fsnotify
612.00 2.2% fsnotify 605.00 2.2% sched_clock_local
596.00 2.1% _raw_spin_unlock_irqrestore 593.00 2.1% system_call_after_swapgs
542.00 1.9% sysret_check 559.00 2.0% sysret_check
467.00 1.7% fget_light 472.00 1.7% fget_light
462.00 1.6% finish_task_switch 461.00 1.7% finish_task_switch
437.00 1.5% vfs_write 442.00 1.6% vfs_write
431.00 1.5% do_sync_write 428.00 1.5% do_sync_write
* 413.00 1.5% select_task_rq_fair 404.00 1.5% _raw_spin_lock_irq
386.00 1.4% update_curr 402.00 1.4% update_curr
385.00 1.4% rw_verify_area 389.00 1.4% do_sync_read
377.00 1.3% _raw_spin_lock_irq 378.00 1.4% vfs_read
369.00 1.3% do_sync_read 340.00 1.2% pipe_iov_copy_from_user
360.00 1.3% vfs_read 316.00 1.1% __wake_up_sync_key
342.00 1.2% hrtick_start_fair 313.00 1.1% __wake_up_common
Signed-off-by: Mike Galbraith <efault@....de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: http://lkml.kernel.org/r/1321971504.6855.15.camel@marge.simson.net
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
kernel/sched/fair.c | 3 +++
kernel/sched/rt.c | 3 +++
2 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 96a9ece..8e534a0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2744,6 +2744,9 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
int want_sd = 1;
int sync = wake_flags & WF_SYNC;
+ if (p->rt.nr_cpus_allowed == 1)
+ return prev_cpu;
+
if (sd_flag & SD_BALANCE_WAKE) {
if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
want_affine = 1;
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 023b355..58a4844 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1200,6 +1200,9 @@ select_task_rq_rt(struct task_struct *p, int sd_flag, int flags)
cpu = task_cpu(p);
+ if (p->rt.nr_cpus_allowed == 1)
+ goto out;
+
/* For anything but wake ups, just return the task_cpu */
if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
goto out;
--
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