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Date: Mon, 27 May 2024 10:05:03 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Mike Galbraith <efault@gmx.de>, kprateek.nayak@amd.com
Cc: Chunxin Zang <spring.cxz@gmail.com>, mingo@redhat.com,
	juri.lelli@redhat.com, vincent.guittot@linaro.org,
	dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com,
	mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com,
	linux-kernel@vger.kernel.org, yu.c.chen@intel.com,
	yangchen11@lixiang.com, zhouchunhua@lixiang.com,
	zangchunxin@lixiang.com
Subject: Re: [PATCH] sched/fair: Reschedule the cfs_rq when current is
 ineligible
Message-ID: <20240527080503.GU22557@noisy.programming.kicks-ass.net>
References: <20240524134011.270861-1-spring.cxz@gmail.com>
 <e17d3d90440997b970067fe9eaf088903c65f41d.camel@gmx.de>
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In-Reply-To: <e17d3d90440997b970067fe9eaf088903c65f41d.camel@gmx.de>

On Sat, May 25, 2024 at 08:41:28AM +0200, Mike Galbraith wrote:

> -	if (pick_eevdf(cfs_rq) == pse)
> -		goto preempt;
> -
> -	return;
> +	if (pick_eevdf(cfs_rq) == se)
> +		return;

Right, this will preempt more.

This is probably going to make Prateek's case worse though. Then again,
I was already leaning to towards not making his stronger slice
protection default, because it simply hurts too much elsewhere.

Still, his observation that placing tasks can move V left which in turn
can cause the just scheduled in current non-eligible and cause
over-scheduling is valid -- just not sure what to do about it yet.