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From: Peter Zijlstra <peterz@infradead.org>
To: Mike Galbraith <mgalbraith@suse.de>
Cc: Chris Mason <clm@fb.com>, Ingo Molnar <mingo@kernel.org>,
	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 17:01:56 +0200	[thread overview]
Message-ID: <20160502150156.GX3408@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1462200604.3736.42.camel@suse.de>

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.

  parent reply	other threads:[~2016-05-02 15:02 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 [this message]
2016-05-02 16:04             ` Ingo Molnar
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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