linux-kernel - Re: [PATCH v4] sched: reorder some fields in struct rq

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Message-ID: <CAP_z_Ch=On+sQdLNc3g9hnRCcRoRWazTe_oN+b7tZpF_-_KPcQ@mail.gmail.com>
Date: Wed, 29 Oct 2025 23:53:55 -0700
From: Blake Jones <blakejones@...gle.com>
To: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, 
	Josh Don <joshdon@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, 
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] sched: reorder some fields in struct rq

Hi Madadi,

On Wed, Oct 29, 2025 at 11:29 PM Madadi Vineeth Reddy
<vineethr@...ux.ibm.com> wrote:
> Quick question about the lock placement: Did you test Peter's suggestion of
> co-locating __lock with the clock fields? If so, how did it compare to keeping
> them separate?

I didn't test it (and thus I didn't make the change). Measuring the
real impact of that change seems sufficiently subtle that I wouldn't
trust any microbenchmarks to tell me anything useful about it. I'd
like to get some data from a real-world deployment of the change, but
that will take some time to set up and gather data from.

Blake