From: Mike Galbraith <umgwanakikbuti@gmail.com>
To: Yuyang Du <yuyang.du@intel.com>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Rabin Vincent <rabin.vincent@axis.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Paul Turner <pjt@google.com>, Ben Segall <bsegall@google.com>
Subject: Re: [PATCH?] Livelock in pick_next_task_fair() / idle_balance()
Date: Fri, 03 Jul 2015 06:42:32 +0200 [thread overview]
Message-ID: <1435898552.6418.14.camel@gmail.com> (raw)
In-Reply-To: <20150702184234.GC5197@intel.com>
On Fri, 2015-07-03 at 02:42 +0800, Yuyang Du wrote:
> But still, I think, even with the above, in idle balancing, pulling until the source
> rq's nr_running == 1 is not just "a short term fix", but should be there permanently
> acting like a last guard with no overhead, why not.
Yeah, seems so. Searching for steal all samples...
(this is all with autogroup)
load_balance: idle - s_run: 0 d_run: 2 s_load: 0 d_load: 3 imb: 23 det_tasks: 2 det_load: 3 zeros: 1
load_balance: idle - s_run: 0 d_run: 2 s_load: 0 d_load: 0 imb: 32 det_tasks: 2 det_load: 0 zeros: 2
load_balance: idle - s_run: 0 d_run: 2 s_load: 0 d_load: 1 imb: 17 det_tasks: 2 det_load: 1 zeros: 1
load_balance: idle - s_run: 0 d_run: 2 s_load: 0 d_load: 37 imb: 22 det_tasks: 2 det_load: 37 zeros: 1
load_balance: idle - s_run: 0 d_run: 2 s_load: 0 d_load: 0 imb: 102 det_tasks: 2 det_load: 0 zeros: 2
load_balance: idle - s_run: 0 d_run: 1 s_load: 0 d_load: 93 imb: 47 det_tasks: 1 det_load: 93 zeros: 0
load_balance: idle - s_run: 0 d_run: 2 s_load: 0 d_load: 202 imb: 125 det_tasks: 2 det_load: 202 zeros: 0
load_balance: idle - s_run: 0 d_run: 2 s_load: 0 d_load: 243 imb: 188 det_tasks: 2 det_load: 243 zeros: 0
load_balance: idle - s_run: 0 d_run: 1 s_load: 0 d_load: 145 imb: 73 det_tasks: 1 det_load: 145 zeros: 0
load_balance: idle - s_run: 0 d_run: 1 s_load: 0 d_load: 46 imb: 24 det_tasks: 1 det_load: 46 zeros: 0
Both varieties of total pilferage (w/wo 0 load tasks involved) seem to
happen only during idle balance, never periodic (yet).
Oddity: make -j8 occasionally stacks/pulls piles of load=dinky.
homer:/sys/kernel/debug/tracing # for i in `seq 1 10`; do cat trace|grep "s_run: 1.*det_tasks: $i.*zeros: 0"|wc -l; done
71634
1567
79
15
1
3
0
2
3
0
homer:/sys/kernel/debug/tracing # cat trace|grep "s_run: 1.*det_tasks: 8.*zeros: 0"
<idle>-0 [002] dNs. 594.973783: load_balance: norm - s_run: 1 d_run: 9 s_load: 67 d_load: 1110 imb: 86 det_tasks: 8 det_load: 86 zeros: 0
<...>-10367 [007] d... 1456.477281: load_balance: idle - s_run: 1 d_run: 8 s_load: 805 d_load: 22 imb: 45 det_tasks: 8 det_load: 22 zeros: 0
homer:/sys/kernel/debug/tracing # cat trace|grep "s_run: 1.*det_tasks: 9.*zeros: 0"
<...>-23317 [004] d... 486.677925: load_balance: idle - s_run: 1 d_run: 9 s_load: 888 d_load: 27 imb: 47 det_tasks: 9 det_load: 27 zeros: 0
<...>-11485 [002] d... 573.411095: load_balance: idle - s_run: 1 d_run: 9 s_load: 124 d_load: 78 imb: 82 det_tasks: 9 det_load: 78 zeros: 0
<...>-23286 [000] d... 1510.378740: load_balance: idle - s_run: 1 d_run: 9 s_load: 102 d_load: 58 imb: 63 det_tasks: 9 det_load: 58 zeros: 0
next prev parent reply other threads:[~2015-07-03 4:42 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-06-30 14:30 [PATCH?] Livelock in pick_next_task_fair() / idle_balance() Rabin Vincent
2015-07-01 5:36 ` Mike Galbraith
2015-07-01 14:55 ` Rabin Vincent
2015-07-01 15:47 ` Mike Galbraith
2015-07-01 20:44 ` Peter Zijlstra
2015-07-01 23:25 ` Yuyang Du
2015-07-02 8:05 ` Mike Galbraith
2015-07-02 1:05 ` Yuyang Du
2015-07-02 10:25 ` Mike Galbraith
2015-07-02 11:40 ` Morten Rasmussen
2015-07-02 19:37 ` Yuyang Du
2015-07-03 9:34 ` Morten Rasmussen
2015-07-03 16:38 ` Peter Zijlstra
2015-07-05 22:31 ` Yuyang Du
2015-07-09 14:32 ` Morten Rasmussen
2015-07-09 23:24 ` Yuyang Du
2015-07-05 20:12 ` Yuyang Du
2015-07-06 17:36 ` Dietmar Eggemann
2015-07-07 11:17 ` Rabin Vincent
2015-07-13 17:43 ` Dietmar Eggemann
2015-07-09 13:53 ` Morten Rasmussen
2015-07-09 22:34 ` Yuyang Du
2015-07-02 10:53 ` Peter Zijlstra
2015-07-02 11:44 ` Morten Rasmussen
2015-07-02 18:42 ` Yuyang Du
2015-07-03 4:42 ` Mike Galbraith [this message]
2015-07-03 16:39 ` Peter Zijlstra
2015-07-05 22:11 ` Yuyang Du
2015-07-09 6:15 ` Stefan Ekenberg
2015-07-26 18:57 ` Yuyang Du
2015-08-03 17:05 ` [tip:sched/core] sched/fair: Avoid pulling all tasks in idle balancing tip-bot for Yuyang Du
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