From: Hillf Danton <dhillf@gmail.com>
To: Mike Galbraith <efault@gmx.de>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@elte.hu>, Paul Turner <pjt@google.com>
Subject: Re: [patch 1/6] sched: use rt.nr_cpus_allowed to recover select_task_rq() cycles
Date: Fri, 18 Nov 2011 23:39:46 +0800 [thread overview]
Message-ID: <CAJd=RBDYmffOoUFt3LuzTUhYgkJhTHzUTxZjcyqoB37j21x7bw@mail.gmail.com> (raw)
In-Reply-To: <1321629441.7080.15.camel@marge.simson.net>
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On Fri, Nov 18, 2011 at 11:17 PM, Mike Galbraith <efault@gmx.de> wrote:
>
> 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.
>
> 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
> Â Â Â Â Â Â _______ _____ ___________________________ _______ _____ ___________________________
>
>       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@gmx.de>
>
Acked-by: Hillf Danton <dhillf@gmail.com>
> ---
> Â kernel/sched_fair.c | Â Â 3 +++
>  kernel/sched_rt.c  |   3 +++
> Â 2 files changed, 6 insertions(+)
>
> Index: linux-3.2.git/kernel/sched_fair.c
> ===================================================================
> --- linux-3.2.git.orig/kernel/sched_fair.c
> +++ linux-3.2.git/kernel/sched_fair.c
> @@ -2340,6 +2340,9 @@ select_task_rq_fair(struct task_struct *
> Â Â Â Â int want_sd = 1;
> Â Â Â Â int sync = wake_flags & WF_SYNC;
>
> + Â Â Â if (p->rt.nr_cpus_allowed < 2)
> + Â Â Â Â Â Â Â return prev_cpu;
> +
> Â Â Â Â if (sd_flag & SD_BALANCE_WAKE) {
> Â Â Â Â Â Â Â Â if (cpumask_test_cpu(cpu, tsk_cpus_allowed(p)))
> Â Â Â Â Â Â Â Â Â Â Â Â want_affine = 1;
> Index: linux-3.2.git/kernel/sched_rt.c
> ===================================================================
> --- linux-3.2.git.orig/kernel/sched_rt.c
> +++ linux-3.2.git/kernel/sched_rt.c
> @@ -999,6 +999,9 @@ select_task_rq_rt(struct task_struct *p,
>
> Â Â Â Â cpu = task_cpu(p);
>
> + Â Â Â if (p->rt.nr_cpus_allowed < 2)
> + Â Â Â Â Â Â Â goto out;
> +
> Â Â Â Â /* For anything but wake ups, just return the task_cpu */
> Â Â Â Â if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
> Â Â Â Â Â Â Â Â goto out;
>
>
> --
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next prev parent reply other threads:[~2011-11-18 15:39 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-15 9:46 sched: Avoid SMT siblings in select_idle_sibling() if possible Peter Zijlstra
2011-11-16 1:14 ` Suresh Siddha
2011-11-16 9:24 ` Mike Galbraith
2011-11-16 18:37 ` Suresh Siddha
2011-11-17 1:59 ` Mike Galbraith
2011-11-17 15:38 ` Mike Galbraith
2011-11-17 15:56 ` Peter Zijlstra
2011-11-17 16:38 ` Mike Galbraith
2011-11-17 17:36 ` Suresh Siddha
2011-11-18 15:14 ` Mike Galbraith
2011-11-18 15:17 ` [patch 1/6] sched: use rt.nr_cpus_allowed to recover select_task_rq() cycles Mike Galbraith
2011-11-18 15:35 ` Peter Zijlstra
2011-11-18 17:34 ` Mike Galbraith
2011-11-22 14:17 ` Mike Galbraith
2011-11-22 14:18 ` [patch 1/7] " Mike Galbraith
2011-12-06 9:50 ` [tip:sched/core] sched: Use " tip-bot for Mike Galbraith
2011-11-22 14:20 ` [patch 2/7] sched: save some hrtick_start_fair cycles Mike Galbraith
2011-12-06 20:20 ` [tip:sched/core] sched: Save " tip-bot for Mike Galbraith
2011-11-22 14:21 ` [patch 3/7] sched: set skip_clock_update in yield_task_fair() Mike Galbraith
2011-11-23 11:53 ` Peter Zijlstra
2011-11-23 12:06 ` Mike Galbraith
2011-11-23 14:48 ` Peter Zijlstra
2011-11-24 3:50 ` Mike Galbraith
2011-11-24 10:12 ` Peter Zijlstra
2011-11-25 6:39 ` Mike Galbraith
2011-12-06 9:51 ` [tip:sched/core] sched: Set " tip-bot for Mike Galbraith
2011-11-22 14:22 ` [patch 4/7] sched: convert rq->avg_idle to rq->avg_event Mike Galbraith
2011-11-23 11:55 ` Peter Zijlstra
2011-11-23 12:09 ` Mike Galbraith
2011-11-23 12:27 ` Peter Zijlstra
2011-11-23 12:57 ` Mike Galbraith
2011-11-23 14:21 ` Mike Galbraith
2011-11-22 14:23 ` [patch 5/7] sched: ratelimit select_idle_sibling()for sync wakeups Mike Galbraith
2011-11-22 14:24 ` [patch 6/7] sched: use rq->avg_event to resurrect nohz ratelimiting Mike Galbraith
2011-11-23 11:57 ` Peter Zijlstra
2011-11-23 12:35 ` Mike Galbraith
2011-11-22 14:26 ` [patch 7/7] sched: only use TTWU_QUEUE when waker/wakee CPUs do not share top level cache Mike Galbraith
2011-11-23 12:08 ` Peter Zijlstra
2011-11-18 15:39 ` Hillf Danton [this message]
2011-11-18 15:18 ` [patch 2/6] sched: convert rq->avg_idle to rq->avg_event Mike Galbraith
2011-11-18 15:19 ` [patch 3/6] sched: use rq->avg_event to resurrect nohz ratelimiting Mike Galbraith
2011-11-18 15:36 ` Peter Zijlstra
2011-11-18 17:42 ` Mike Galbraith
2011-11-19 0:51 ` Van De Ven, Arjan
2011-11-19 4:15 ` Mike Galbraith
2011-11-18 15:20 ` [patch 4/6] sched: ratelimit select_idle_sibling()for sync wakeups Mike Galbraith
2011-11-18 15:22 ` [patch 5/6] sched: save some hrtick_start_fair cycles Mike Galbraith
2011-11-18 15:23 ` [patch 6/6] sched: set skip_clock_update in yield_task_fair() Mike Galbraith
2012-02-20 14:41 ` sched: Avoid SMT siblings in select_idle_sibling() if possible Peter Zijlstra
2012-02-20 15:03 ` Srivatsa Vaddagiri
2012-02-20 18:25 ` Mike Galbraith
2012-02-21 0:06 ` Srivatsa Vaddagiri
2012-02-21 6:37 ` Mike Galbraith
2012-02-21 8:09 ` Srivatsa Vaddagiri
2012-02-20 18:14 ` Mike Galbraith
2012-02-20 18:15 ` Peter Zijlstra
2012-02-20 19:07 ` Peter Zijlstra
2012-02-21 5:43 ` Mike Galbraith
2012-02-21 8:32 ` Srivatsa Vaddagiri
2012-02-21 9:21 ` Mike Galbraith
2012-02-21 10:37 ` Peter Zijlstra
2012-02-21 14:58 ` Srivatsa Vaddagiri
2012-02-23 10:49 ` Srivatsa Vaddagiri
2012-02-23 11:19 ` Ingo Molnar
2012-02-23 12:18 ` Srivatsa Vaddagiri
2012-02-23 11:20 ` Srivatsa Vaddagiri
2012-02-23 11:26 ` Ingo Molnar
2012-02-23 11:32 ` Srivatsa Vaddagiri
2012-02-23 16:17 ` Ingo Molnar
2012-02-23 11:21 ` Mike Galbraith
2012-02-25 6:54 ` Srivatsa Vaddagiri
2012-02-25 8:30 ` Mike Galbraith
2012-02-27 22:11 ` Suresh Siddha
2012-02-28 5:05 ` Mike Galbraith
2011-11-17 19:08 ` Suresh Siddha
2011-11-18 15:12 ` Peter Zijlstra
2011-11-18 15:26 ` Mike Galbraith
2011-12-06 9:49 ` [tip:sched/core] sched: Clean up domain traversal in select_idle_sibling() tip-bot for Suresh Siddha
2011-11-18 23:40 ` [tip:sched/core] sched: Avoid SMT siblings in select_idle_sibling() if possible tip-bot for Peter Zijlstra
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