From: Viresh Kumar <viresh.kumar@linaro.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org,
Vincent Guittot <vincent.guittot@linaro.org>,
tkjos@google.com, Daniel Lezcano <daniel.lezcano@linaro.org>,
quentin.perret@linaro.org, chris.redpath@arm.com,
steven.sistare@oracle.com, subhra.mazumdar@oracle.com,
songliubraving@fb.com
Subject: Re: [PATCH V3 0/2] sched/fair: Fallback to sched-idle CPU in absence of idle CPUs
Date: Wed, 3 Jul 2019 14:43:31 +0530 [thread overview]
Message-ID: <20190703091331.gnoouol3hn77r65b@vireshk-i7> (raw)
In-Reply-To: <20190701134343.GT3402@hirez.programming.kicks-ass.net>
On 01-07-19, 15:43, Peter Zijlstra wrote:
> On Wed, Jun 26, 2019 at 10:36:28AM +0530, Viresh Kumar wrote:
> > Hi,
> >
> > We try to find an idle CPU to run the next task, but in case we don't
> > find an idle CPU it is better to pick a CPU which will run the task the
> > soonest, for performance reason.
> >
> > A CPU which isn't idle but has only SCHED_IDLE activity queued on it
> > should be a good target based on this criteria as any normal fair task
> > will most likely preempt the currently running SCHED_IDLE task
> > immediately. In fact, choosing a SCHED_IDLE CPU over a fully idle one
> > shall give better results as it should be able to run the task sooner
> > than an idle CPU (which requires to be woken up from an idle state).
> >
> > This patchset updates both fast and slow paths with this optimization.
>
> So this basically does the trivial SCHED_IDLE<-* wakeup preemption test;
Right.
> one could consider doing the full wakeup preemption test instead.
I am not sure what you meant by "full wakeup preemption test" :(
> Now; the obvious argument against doing this is cost; esp. the cgroup
> case is very expensive I suppose. But it might be a fun experiment to
> try.
> That said; I'm tempted to apply these patches..
Please do, who is stopping you :)
--
viresh
next prev parent reply other threads:[~2019-07-03 9:13 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-26 5:06 [PATCH V3 0/2] sched/fair: Fallback to sched-idle CPU in absence of idle CPUs Viresh Kumar
2019-06-26 5:06 ` [PATCH V3 1/2] sched: Start tracking SCHED_IDLE tasks count in cfs_rq Viresh Kumar
2019-07-25 16:15 ` [tip:sched/core] sched/fair: " tip-bot for Viresh Kumar
2019-06-26 5:06 ` [PATCH V3 2/2] sched/fair: Fallback to sched-idle CPU if idle CPU isn't found Viresh Kumar
2019-06-29 1:16 ` Subhra Mazumdar
2019-07-01 8:03 ` Viresh Kumar
2019-07-01 22:08 ` Subhra Mazumdar
2019-07-02 8:35 ` Peter Zijlstra
2019-07-02 16:32 ` Subhra Mazumdar
2019-07-25 16:16 ` [tip:sched/core] sched/fair: Fall back " tip-bot for Viresh Kumar
2019-07-01 13:43 ` [PATCH V3 0/2] sched/fair: Fallback to sched-idle CPU in absence of idle CPUs Peter Zijlstra
2019-07-03 9:13 ` Viresh Kumar [this message]
2019-12-09 3:50 ` Wanpeng Li
2019-12-10 6:33 ` Viresh Kumar
2019-12-10 11:15 ` Wanpeng Li
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