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Date: Tue, 15 Nov 2022 16:02:00 +0000 From: Joel Fernandes <joel@...lfernandes.org> To: Connor O'Brien <connoro@...gle.com> Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com, John Stultz <jstultz@...gle.com>, Qais Yousef <qais.yousef@....com>, Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira <bristot@...hat.com>, Valentin Schneider <vschneid@...hat.com>, Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>, "Paul E . McKenney" <paulmck@...nel.org> Subject: Re: [RFC PATCH 10/11] torture: support randomized shuffling for proxy exec testing On Mon, Nov 14, 2022 at 12:44:21PM -0800, Connor O'Brien wrote: > > Instead of doing it this way, maybe another approach is to randomize the > > sleep interval in: > > > > */ > > static int torture_shuffle(void *arg) > > { > > VERBOSE_TOROUT_STRING("torture_shuffle task started"); > > do { > > schedule_timeout_interruptible(shuffle_interval); > > torture_shuffle_tasks(); > > ... > > } while (...) > > ... > > } > > > > Right now with this patch you still wakeup the shuffle thread when skipping > > the affinity set operation. > > > > thanks, > > > > - Joel > > > > Wouldn't the affinities of all the tasks still change in lockstep > then? The intent with this patch is to get into situations where the > tasks have different affinity masks, which I think requires changing > the behavior of torture_shuffle_tasks() rather than how often it's > called. Correct me if I'm wrong, but you are still changing the affinities of all the tasks at the same time (shuffle_task_list still has all the threads being set to the same affinity). The difference is with your patch, you occasionally skip punching a consecutive hole into shuffle_tmp_mask. I was thinking how you could make this patch more upstreamable, you are right calling less often is not what you are specifically looking for. However, would a better approach be to: a) randomize the shuffle duration. b) Instead of skipping the set_cpus_allowed_ptr(), why not randomize the number of times you call cpumask_next() to pick a random hole. These are just some ideas. thanks, - Joel
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