linux-kernel - Re: [PATCH 3/3] sched/core: Indicate a sched_delayed task was migrated before wakeup

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Message-ID: <2b211cf7-4800-564d-d39c-8013081afee0@amd.com>
Date: Tue, 15 Oct 2024 08:41:32 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Johannes Weiner <hannes@...xchg.org>, Peter Zijlstra
	<peterz@...radead.org>
CC: Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>, Suren Baghdasaryan
	<surenb@...gle.com>, <linux-kernel@...r.kernel.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>, Thomas Gleixner <tglx@...utronix.de>, Klaus Kudielka
	<klaus.kudielka@...il.com>, Chris Bainbridge <chris.bainbridge@...il.com>,
	"Linux regression tracking (Thorsten Leemhuis)" <regressions@...mhuis.info>,
	"Gautham R. Shenoy" <gautham.shenoy@....com>, Youssef Esmat
	<youssefesmat@...gle.com>, Paul Menzel <pmenzel@...gen.mpg.de>, "Bert
 Karwatzki" <spasswolf@....de>, <regressions@...ts.linux.dev>
Subject: Re: [PATCH 3/3] sched/core: Indicate a sched_delayed task was
 migrated before wakeup

Hello Johannes,

On 10/14/2024 8:13 PM, Johannes Weiner wrote:
> On Fri, Oct 11, 2024 at 12:39:58PM +0200, Peter Zijlstra wrote:
>> On Fri, Oct 11, 2024 at 06:08:03AM -0400, Johannes Weiner wrote:
>>> Completely untested. But if it looks good, I'll send a proper patch.
>>
>> Sure. Thanks for doing this.
> 
> Ok here goes. Built, booted and runtime-tested.
> 
> ---
> 
>  From 91f230caa0119877cb861047e1af1371bf00d908 Mon Sep 17 00:00:00 2001
> From: Johannes Weiner <hannes@...xchg.org>
> Date: Fri, 11 Oct 2024 06:18:07 -0400
> Subject: [PATCH] sched: psi: pass enqueue/dequeue flags to psi callbacks
>   directly
> 
> What psi needs to do on each enqueue and dequeue has gotten more
> subtle, and the generic sched code trying to distill this into a bool
> for the callbacks is awkward.
> 
> Pass the flags directly and let psi parse them. For that to work, the
> #include "stats.h" (which has the psi callback implementations) needs
> to be below the flag definitions in "sched.h". Move that section
> further down, next to some of the other accounting stuff.
> 
> This also puts the ENQUEUE_SAVE/RESTORE branch behind the psi jump
> label, slightly reducing overhead when PSI=y but runtime disabled.
> 
> Link: https://lore.kernel.org/lkml/20241011083323.GL17263@noisy.programming.kicks-ass.net/
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

I tested this series on top of tip:sched/urgent at commit cd9626e9ebc7
("sched/fair: Fix external p->on_rq users") and did not observe any
splats related to PSI or otherwise. Please feel free to add:

Tested-by: K Prateek Nayak <kprateek.nayak@....com>

-- 
Thanks and Regards,
Prateek

> ---
>   kernel/sched/core.c  | 12 +++++-----
>   kernel/sched/sched.h | 56 ++++++++++++++++++++++----------------------
>   kernel/sched/stats.h | 29 +++++++++++++++--------
>   3 files changed, 53 insertions(+), 44 deletions(-)
> 
> [..snip..]