From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Valentin Schneider <vschneid@redhat.com>,
Will Deacon <will@kernel.org>, Phil Auld <pauld@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] sched: Store restrict_cpus_allowed_ptr() call state
Date: Mon, 30 Jan 2023 14:05:33 -0500 [thread overview]
Message-ID: <b708c5bc-8b06-3c7a-17e9-38e0220cdb32@redhat.com> (raw)
In-Reply-To: <Y9eweBuHFeO1jZCH@hirez.programming.kicks-ass.net>
On 1/30/23 06:56, Peter Zijlstra wrote:
> On Thu, Jan 26, 2023 at 08:55:27PM -0500, Waiman Long wrote:
>> The user_cpus_ptr field was originally added by commit b90ca8badbd1
>> ("sched: Introduce task_struct::user_cpus_ptr to track requested
>> affinity"). It was used only by arm64 arch due to possible asymmetric
>> CPU setup.
>>
>> Since commit 8f9ea86fdf99 ("sched: Always preserve the user requested
>> cpumask"), task_struct::user_cpus_ptr is repurposed to store user
>> requested cpu affinity specified in the sched_setaffinity().
>>
>> This results in a slight performance regression on an arm64
>> system when booted with "allow_mismatched_32bit_el0"
> Dude, how can you still call this a slight performance regression after
> Will told you time and time again that's not the problem.
>
> It clearly is a behavioural problem.
I am trying to figure out if this behavioral problem is a result of my
scheduler patch or just as a result of cgroup v1 current behavior as I
don't see how my patch will cause this behavioral change if it is not an
existing problem.
Cheers,
Longman
prev parent reply other threads:[~2023-01-30 19:06 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-27 1:55 Waiman Long
2023-01-27 10:12 ` Linux kernel regression tracking (Thorsten Leemhuis)
2023-01-27 12:59 ` Will Deacon
2023-01-27 14:54 ` Waiman Long
2023-01-28 15:19 ` kernel test robot
2023-01-30 11:56 ` Peter Zijlstra
2023-01-30 19:05 ` Waiman Long [this message]
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