From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Mel Gorman <mgorman@techsingularity.net>,
"Li, Aubrey" <aubrey.li@linux.intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Qais Yousef <qais.yousef@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
Jiang Biao <benbjiang@gmail.com>
Subject: Re: [RFC][PATCH 1/5] sched/fair: Fix select_idle_cpu()s cost accounting
Date: Fri, 8 Jan 2021 20:49:33 +0100 [thread overview]
Message-ID: <X/i3TbRRS9chYb3l@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAKfTPtCGCmCv0yXSUmYUh6=8uzd0n9xFPqC0cW4sm-FqDvjvCQ@mail.gmail.com>
On Fri, Jan 08, 2021 at 04:10:51PM +0100, Vincent Guittot wrote:
> Another thing that worries me, is that we use the avg_idle of the
> local cpu, which is obviously not idle otherwise it would have been
> selected, to decide how much time we should spend on looking for
> another idle CPU. I'm not sure that's the right metrics to use
> especially with a possibly stalled value.
The thinking was that if this CPU has little idle time, this CPU should
not spend a lot of time searching...
That is; if we spend more time looking for places to run, than we have
idle time, we're loosing cycles we could've ran (supposedly useful) work.
The only counter argument is tail latency.
next prev parent reply other threads:[~2021-01-08 19:50 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-14 16:48 [RFC][PATCH 0/5] select_idle_sibling() wreckage Peter Zijlstra
2020-12-14 16:48 ` [RFC][PATCH 1/5] sched/fair: Fix select_idle_cpu()s cost accounting Peter Zijlstra
2020-12-15 3:36 ` Li, Aubrey
2020-12-15 7:59 ` Peter Zijlstra
2020-12-15 11:45 ` Mel Gorman
2020-12-15 12:13 ` Li, Aubrey
2021-01-08 10:27 ` Mel Gorman
2021-01-08 13:01 ` Qais Yousef
2021-01-08 13:47 ` Mel Gorman
2021-01-08 13:41 ` Vincent Guittot
2021-01-08 14:40 ` Mel Gorman
2021-01-08 15:10 ` Vincent Guittot
2021-01-08 16:14 ` Mel Gorman
2021-01-11 14:36 ` Vincent Guittot
2021-01-11 15:58 ` Mel Gorman
2021-01-08 19:45 ` Peter Zijlstra
2021-01-09 14:12 ` Mel Gorman
2021-01-11 14:39 ` Vincent Guittot
2021-01-08 19:49 ` Peter Zijlstra [this message]
2021-01-11 14:52 ` Vincent Guittot
2021-01-08 20:21 ` Peter Zijlstra
2021-01-09 13:59 ` Mel Gorman
2020-12-14 16:48 ` [RFC][PATCH 2/5] sched/fair: Make select_idle_cpu() proportional to cores Peter Zijlstra
2020-12-23 13:31 ` Vincent Guittot
2020-12-14 16:48 ` [RFC][PATCH 3/5] sched/fair: Remove select_idle_smt() Peter Zijlstra
2020-12-14 16:48 ` [RFC][PATCH 4/5] sched/fair: Merge select_idle_core/cpu() Peter Zijlstra
2020-12-14 16:48 ` [RFC][PATCH 5/5] sched/fair: SIS_PROP the idle core scan Peter Zijlstra
2020-12-16 12:59 ` [RFC][PATCH 0/5] select_idle_sibling() wreckage Li, Aubrey
2020-12-16 18:07 ` Vincent Guittot
2020-12-23 13:23 ` Vincent Guittot
2021-01-04 15:40 ` Mel Gorman
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