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From: Chen Yu <yu.chen.surf@gmail.com>
To: Tim Chen <tim.c.chen@linux.intel.com>
Cc: kernel test robot <oliver.sang@intel.com>,
	0day robot <lkp@intel.com>, Chen Yu <yu.c.chen@intel.com>,
	Walter Mack <walter.mack@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	lkp@lists.01.org, Huang Ying <ying.huang@intel.com>,
	feng.tang@intel.com, zhengjun.xing@linux.intel.com,
	fengwei.yin@intel.com, Peter Zijlstra <peterz@infradead.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Ingo Molnar <mingo@elte.hu>, Juri Lelli <juri.lelli@redhat.com>,
	Mel Gorman <mgorman@suse.de>,
	Aubrey Li <aubrey.li@linux.intel.com>
Subject: Re: [sched/fair] ddb3b1126f: hackbench.throughput -25.9% regression
Date: Sat, 2 Apr 2022 02:04:09 +0800	[thread overview]
Message-ID: <CADjb_WQsTkdbwrvtzWwjt2O_jiuQTx+=Xy=yMPbAwKPmFDX-0w@mail.gmail.com> (raw)
In-Reply-To: <7aa67fedb4b6dc9126bc59ee993fa18d0e472475.camel@linux.intel.com>

On Thu, Mar 31, 2022 at 11:42 AM Tim Chen <tim.c.chen@linux.intel.com> wrote:
>
> On Wed, 2022-03-30 at 17:46 +0800, kernel test robot wrote:
> >
> > Greeting,
> >
> > FYI, we noticed a -25.9% regression of hackbench.throughput due to commit:
> >
>
> Will try to check the regression seen.
>
Double check  that the regression could be reproduced on top of the
latest sched/core branch:
parent ("sched/fair: Don't rely on ->exec_start for migration")
fbc  ("sched/fair: Simple runqueue order on migrate")

parent                                fbc
91107           -40.8%      53897        hackbench.throughput

and it is consistent with lkp's original report that the  context
switch count is much higher with patch applied:
9591919          +510.3%   58534937
hackbench.time.involuntary_context_switches
36451523          +281.5%  1.391e+08
hackbench.time.voluntary_context_switches

Considering that this patch  'raises' the priority of the migrated
task, by giving it the cfs_rq->min_vruntime,
it is possible that the migrated task would preempt the current
running task more easily.

0.00           +12.2       12.21
perf-profile.calltrace.cycles-pp.enqueue_entity.enqueue_task_fair.ttwu_do_activate.try_to_wake_up.autoremove_wake_function
and the patched version has  spent more time on enqueue_entity(),
which might be caused by setting sched entity hierarchy from leaf to
root,
which was mentioned in another thread.

-- 
Thanks,
Chenyu

WARNING: multiple messages have this Message-ID (diff)
From: Chen Yu <yu.chen.surf@gmail.com>
To: lkp@lists.01.org
Subject: Re: [sched/fair] ddb3b1126f: hackbench.throughput -25.9% regression
Date: Sat, 02 Apr 2022 02:04:09 +0800	[thread overview]
Message-ID: <CADjb_WQsTkdbwrvtzWwjt2O_jiuQTx+=Xy=yMPbAwKPmFDX-0w@mail.gmail.com> (raw)
In-Reply-To: <7aa67fedb4b6dc9126bc59ee993fa18d0e472475.camel@linux.intel.com>

[-- Attachment #1: Type: text/plain, Size: 1482 bytes --]

On Thu, Mar 31, 2022 at 11:42 AM Tim Chen <tim.c.chen@linux.intel.com> wrote:
>
> On Wed, 2022-03-30 at 17:46 +0800, kernel test robot wrote:
> >
> > Greeting,
> >
> > FYI, we noticed a -25.9% regression of hackbench.throughput due to commit:
> >
>
> Will try to check the regression seen.
>
Double check  that the regression could be reproduced on top of the
latest sched/core branch:
parent ("sched/fair: Don't rely on ->exec_start for migration")
fbc  ("sched/fair: Simple runqueue order on migrate")

parent                                fbc
91107           -40.8%      53897        hackbench.throughput

and it is consistent with lkp's original report that the  context
switch count is much higher with patch applied:
9591919          +510.3%   58534937
hackbench.time.involuntary_context_switches
36451523          +281.5%  1.391e+08
hackbench.time.voluntary_context_switches

Considering that this patch  'raises' the priority of the migrated
task, by giving it the cfs_rq->min_vruntime,
it is possible that the migrated task would preempt the current
running task more easily.

0.00           +12.2       12.21
perf-profile.calltrace.cycles-pp.enqueue_entity.enqueue_task_fair.ttwu_do_activate.try_to_wake_up.autoremove_wake_function
and the patched version has  spent more time on enqueue_entity(),
which might be caused by setting sched entity hierarchy from leaf to
root,
which was mentioned in another thread.

-- 
Thanks,
Chenyu

  reply	other threads:[~2022-04-01 18:04 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-25 22:54 [PATCH 0/2] sched/fair: Fix starvation caused by task migration Tim Chen
2022-03-25 22:54 ` [PATCH 1/2] sched/fair: Don't rely on ->exec_start for migration Tim Chen
2022-03-25 22:54 ` [PATCH 2/2] sched/fair: Simple runqueue order on migrate Tim Chen
2022-03-29  9:03   ` Vincent Guittot
2022-03-31 11:47     ` Peter Zijlstra
2022-03-31 12:15       ` Vincent Guittot
2022-03-29 10:09   ` Abel Wu
2022-03-29 14:26     ` Tim Chen
2022-03-30  9:46   ` [sched/fair] ddb3b1126f: hackbench.throughput -25.9% regression kernel test robot
2022-03-30  9:46     ` kernel test robot
2022-03-30 23:48     ` Tim Chen
2022-03-30 23:48       ` Tim Chen
2022-04-01 18:04       ` Chen Yu [this message]
2022-04-01 18:04         ` Chen Yu

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