linux-kernel - Re: [PATCH] sched/task_struct: Move alloc

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Message-ID: <20240630211142.kZAs9f0p@linutronix.de>
Date: Sun, 30 Jun 2024 23:11:42 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ben Segall <bsegall@...gle.com>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
	Klara Modin <klarasmodin@...il.com>, Mel Gorman <mgorman@...e.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH] sched/task_struct: Move alloc_tag to the end of the
 struct.

On 2024-06-28 16:20:27 [-0400], Kent Overstreet wrote:
> > Kent, you said you didn't want it where it currently is. Fine. You said
> > you want it at the front next to `flags'. This isn't going to work since
> > there is no space left. You didn't make another suggestion or say how to
> > make room.
> 
> It doesn't need to be on the exact same cacheline, just as near as you
> can get it.

the first possible thing would be somewhere after the scheduler.
However, what difference does it make if it s two cache lines later or
more?  I don't understand the requirement "closer".

Sebastian