linux-kernel - Re: [PATCH 2/2] sched/fair: Fix premature check of WAKEUP

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Message-ID: <61589e0e-a3d7-490c-8bba-a1ce25f585c3@linux.alibaba.com>
Date: Tue, 25 Feb 2025 14:56:52 +0800
From: Tianchen Ding <dtcccc@...ux.alibaba.com>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Juri Lelli <juri.lelli@...hat.com>,
 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>,
 Josh Don <joshdon@...gle.com>,
 "open list:SCHEDULER" <linux-kernel@...r.kernel.org>,
 Abel Wu <wuyun.abel@...edance.com>
Subject: Re: [PATCH 2/2] sched/fair: Fix premature check of WAKEUP_PREEMPTION



On 2/24/25 9:47 PM, Vincent Guittot wrote:
[...]
> 
> Or we should just remove it. I'm curious to know who used it during
> the last couple of years ? Having in mind that lazy preemption adds
> another level as check_preempt_wakeup_fair()  uses it so sched-idle
> tasks might not always be immediately preempted anyway.
> 

I just remembered that I've mentioned this issue in another thread[1] 
before. Can we do preempt SCHED_IDLE immediately even in PREEMPT_LAZY? (to 
achieve better response time for SCHED_NORMAL)

[1] 
https://lore.kernel.org/all/8e6f02a0-2bd0-4e75-9055-2cb7c508ce4e@linux.alibaba.com/