From: Peter Zijlstra <peterz@infradead.org>
To: Quentin Perret <qperret@google.com>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>,
linux-kernel@vger.kernel.org, aaron.lwe@gmail.com,
valentin.schneider@arm.com, mingo@kernel.org, pauld@redhat.com,
jdesfossez@digitalocean.com, naravamudan@digitalocean.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
juri.lelli@redhat.com, rostedt@goodmis.org, bsegall@google.com,
mgorman@suse.de, kernel-team@android.com, john.stultz@linaro.org
Subject: Re: NULL pointer dereference in pick_next_task_fair
Date: Fri, 8 Nov 2019 13:24:47 +0100 [thread overview]
Message-ID: <20191108122447.GQ5671@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20191108120034.GK4131@hirez.programming.kicks-ass.net>
On Fri, Nov 08, 2019 at 01:00:34PM +0100, Peter Zijlstra wrote:
> > That would remove one call site to newidle_balance() too, which I think
> > is good. Hackbench probably won't like that, though.
>
> Yeah, that fast path really is important. I've got a few patches pending
> there, fixing a few things and that gets me 2% extra on a sched-yield
> benchmark.
That is, the fast path also allows a cpu-cgroup optimization that wins
something in the order of 3% for cgroup workloads.
The cgroup optimization is basically that when we schedule from
fair->fair, we can avoid having to put/set the whole cgroup hierarchy
but only have to update the part that changed.
Couple that with the set_next_buddy() from dequeue_task_fair(), which
results in the next task being more likely to be from the same cgroup,
and you've got a win.
next prev parent reply other threads:[~2019-11-08 12:25 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-28 17:46 Quentin Perret
2019-10-28 21:49 ` Peter Zijlstra
2019-10-29 11:34 ` Peter Zijlstra
2019-10-29 11:50 ` Quentin Perret
2019-10-30 22:50 ` Ram Muthiah
2019-10-31 1:33 ` Valentin Schneider
2019-10-31 10:54 ` Valentin Schneider
2019-10-31 14:24 ` Valentin Schneider
2019-10-31 22:15 ` Valentin Schneider
2019-11-06 12:05 ` Peter Zijlstra
2019-11-06 13:08 ` Peter Zijlstra
2019-11-06 15:04 ` Qais Yousef
2019-11-06 16:57 ` Peter Zijlstra
2019-11-06 17:26 ` Qais Yousef
2019-11-06 15:51 ` Kirill Tkhai
2019-11-06 16:54 ` Peter Zijlstra
2019-11-06 17:27 ` Peter Zijlstra
2019-11-07 8:36 ` Kirill Tkhai
2019-11-07 13:26 ` Peter Zijlstra
2019-11-07 15:12 ` Kirill Tkhai
2019-11-07 15:42 ` Peter Zijlstra
2019-11-07 15:53 ` Kirill Tkhai
2019-11-07 15:38 ` Quentin Perret
2019-11-07 18:43 ` Peter Zijlstra
2019-11-07 19:27 ` Quentin Perret
2019-11-07 19:31 ` Peter Zijlstra
2019-11-07 19:42 ` Quentin Perret
2019-11-07 19:29 ` Peter Zijlstra
2019-11-08 11:02 ` Quentin Perret
2019-11-08 11:47 ` Valentin Schneider
2019-11-08 11:58 ` Quentin Perret
2019-11-08 12:00 ` Peter Zijlstra
2019-11-08 12:15 ` Quentin Perret
2019-11-08 12:35 ` Peter Zijlstra
2019-11-08 12:24 ` Peter Zijlstra [this message]
2019-11-08 11:55 ` Peter Zijlstra
2019-11-08 12:52 ` Peter Zijlstra
2019-11-07 16:09 ` Qais Yousef
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