From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <mgalbraith@suse.de>, Chris Mason <clm@fb.com>,
Matt Fleming <matt@codeblueprint.co.uk>,
linux-kernel@vger.kernel.org
Subject: Re: sched: tweak select_idle_sibling to look for idle threads
Date: Mon, 2 May 2016 18:04:04 +0200 [thread overview]
Message-ID: <20160502160403.GA15153@gmail.com> (raw)
In-Reply-To: <20160502150156.GX3408@twins.programming.kicks-ass.net>
* Peter Zijlstra <peterz@infradead.org> wrote:
> On Mon, May 02, 2016 at 04:50:04PM +0200, Mike Galbraith wrote:
> > On Mon, 2016-05-02 at 10:46 +0200, Peter Zijlstra wrote:
> > 5226 /*
> > 5227 * If there are idle cores to be had, go find one.
> > 5228 */
> > 5229 if (sched_feat(IDLE_CORE) && test_idle_cores(target)) {
> > 5230 i = select_idle_core(p, target);
> > 5231 if ((unsigned)i < nr_cpumask_bits)
> > 5232 return i;
> > 5233
> > 5234 /*
> > 5235 * Failed to find an idle core; stop looking for one.
> > 5236 */
> > 5237 clear_idle_cores(target);
> > 5238 }
> > 5239 #if 1
> > 5240 for_each_cpu(i, cpu_smt_mask(target)) {
> > 5241 if (idle_cpu(i))
> > 5242 return i;
> > 5243 }
> > 5244
> > 5245 return target;
> > 5246 #endif
>
> And yes, I have a variant of that, that does indeed work way better than
> scanning the whole LLC domain for idle threads.
>
> If you want a laugh, modify select_idle_core() to remember the last idle
> thread it encounters and have it return that when it fails to find an
> idle core.. I'm still stumped to explain why it behaves the way it does.
Assuming by 'behaving the way it does' means it improves things, such a dynamic
with history/memory could be disrupting escalating feedback loops. Only guessing
though.
Thanks,
Ingo
next prev parent reply other threads:[~2016-05-02 16:04 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-05 18:08 [PATCH RFC] select_idle_sibling experiments Chris Mason
2016-04-05 18:43 ` Bastien Bastien Philbert
2016-04-05 19:28 ` Chris Mason
2016-04-05 20:03 ` Matt Fleming
2016-04-05 21:05 ` Bastien Philbert
2016-04-06 0:44 ` Chris Mason
2016-04-06 7:27 ` Mike Galbraith
2016-04-06 13:36 ` Chris Mason
2016-04-09 17:30 ` Chris Mason
2016-04-12 21:45 ` Matt Fleming
2016-04-13 3:40 ` Mike Galbraith
2016-04-13 15:54 ` Chris Mason
2016-04-28 12:00 ` Peter Zijlstra
2016-04-28 13:17 ` Mike Galbraith
2016-05-02 5:35 ` Mike Galbraith
2016-04-07 15:17 ` Chris Mason
2016-04-09 19:05 ` sched: tweak select_idle_sibling to look for idle threads Chris Mason
2016-04-10 10:04 ` Mike Galbraith
2016-04-10 12:35 ` Chris Mason
2016-04-10 12:46 ` Mike Galbraith
2016-04-10 19:55 ` Chris Mason
2016-04-11 4:54 ` Mike Galbraith
2016-04-12 0:30 ` Chris Mason
2016-04-12 4:44 ` Mike Galbraith
2016-04-12 13:27 ` Chris Mason
2016-04-12 18:16 ` Mike Galbraith
2016-04-12 20:07 ` Chris Mason
2016-04-13 3:18 ` Mike Galbraith
2016-04-13 13:44 ` Chris Mason
2016-04-13 14:22 ` Mike Galbraith
2016-04-13 14:36 ` Chris Mason
2016-04-13 15:05 ` Mike Galbraith
2016-04-13 15:34 ` Mike Galbraith
2016-04-30 12:47 ` Peter Zijlstra
2016-05-01 7:12 ` Mike Galbraith
2016-05-01 8:53 ` Peter Zijlstra
2016-05-01 9:20 ` Mike Galbraith
2016-05-07 1:24 ` Yuyang Du
2016-05-08 8:08 ` Mike Galbraith
2016-05-08 18:57 ` Yuyang Du
2016-05-09 3:45 ` Mike Galbraith
2016-05-08 20:22 ` Yuyang Du
2016-05-09 7:44 ` Mike Galbraith
2016-05-09 1:13 ` Yuyang Du
2016-05-09 9:39 ` Mike Galbraith
2016-05-09 23:26 ` Yuyang Du
2016-05-10 7:49 ` Mike Galbraith
2016-05-10 15:26 ` Mike Galbraith
2016-05-10 19:16 ` Yuyang Du
2016-05-11 4:17 ` Mike Galbraith
2016-05-11 1:23 ` Yuyang Du
2016-05-11 9:56 ` Mike Galbraith
2016-05-18 6:41 ` Mike Galbraith
2016-05-09 3:52 ` Mike Galbraith
2016-05-08 20:31 ` Yuyang Du
2016-05-02 8:46 ` Peter Zijlstra
2016-05-02 14:50 ` Mike Galbraith
2016-05-02 14:58 ` Peter Zijlstra
2016-05-02 15:47 ` Chris Mason
2016-05-03 14:32 ` Peter Zijlstra
2016-05-03 15:11 ` Chris Mason
2016-05-04 10:37 ` Peter Zijlstra
2016-05-04 15:31 ` Peter Zijlstra
2016-05-05 22:03 ` Matt Fleming
2016-05-06 18:54 ` Mike Galbraith
2016-05-09 8:33 ` Peter Zijlstra
2016-05-09 8:56 ` Mike Galbraith
2016-05-04 15:45 ` Peter Zijlstra
2016-05-04 17:46 ` Chris Mason
2016-05-05 9:33 ` Peter Zijlstra
2016-05-05 13:58 ` Chris Mason
2016-05-06 7:12 ` Peter Zijlstra
2016-05-06 17:27 ` Chris Mason
2016-05-06 7:25 ` Peter Zijlstra
2016-05-02 17:30 ` Mike Galbraith
2016-05-02 15:01 ` Peter Zijlstra
2016-05-02 16:04 ` Ingo Molnar [this message]
2016-05-03 11:31 ` Peter Zijlstra
2016-05-03 18:22 ` Peter Zijlstra
2016-05-02 15:10 ` Peter Zijlstra
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