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Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tArnL-0000000D5Pj-0rBT; Tue, 12 Nov 2024 14:23:03 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 8F59F300478; Tue, 12 Nov 2024 15:23:02 +0100 (CET) Date: Tue, 12 Nov 2024 15:23:02 +0100 From: Peter Zijlstra To: Phil Auld Cc: Mike Galbraith , mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, kprateek.nayak@amd.com, wuyun.abel@bytedance.com, youssefesmat@chromium.org, tglx@linutronix.de Subject: Re: [PATCH] sched/fair: Dequeue sched_delayed tasks when waking to a busy CPU Message-ID: <20241112142302.GI6497@noisy.programming.kicks-ass.net> References: <20241106135346.GL24862@noisy.programming.kicks-ass.net> <20241106141420.GZ33184@noisy.programming.kicks-ass.net> <982456f0abca321b874b7974bdf17d1a605c3d38.camel@gmx.de> <5280774bce7343c43904ae3df4403942092f5562.camel@gmx.de> <20241107140945.GA34695@noisy.programming.kicks-ass.net> <750542452c4f852831e601e1b8de40df4b108d9a.camel@gmx.de> <5a4cb3e4ab698fe2d8419e28d61e292dcd0c8fad.camel@gmx.de> <20241112124117.GA336451@pauld.westford.csb> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20241112124117.GA336451@pauld.westford.csb> On Tue, Nov 12, 2024 at 07:41:17AM -0500, Phil Auld wrote: > On Tue, Nov 12, 2024 at 08:05:04AM +0100 Mike Galbraith wrote: > > On Fri, 2024-11-08 at 01:24 +0100, Mike Galbraith wrote: > > > On Thu, 2024-11-07 at 15:09 +0100, Peter Zijlstra wrote: > > > > On Thu, Nov 07, 2024 at 03:02:36PM +0100, Mike Galbraith wrote: > > > > > On Thu, 2024-11-07 at 10:46 +0100, Mike Galbraith wrote: > > > > > > On Thu, 2024-11-07 at 05:03 +0100, Mike Galbraith wrote: > > > > > > > > > > > > > > I built that patch out of curiosity, and yeah, set_next_task_fair() > > > > > > > finding a cfs_rq->curr ends play time pretty quickly. > > > > > > > > > > > > The below improved uptime, and trace_printk() says it's doing the > > > > > > intended, so I suppose I'll add a feature and see what falls out. > > > > > > > > > > From netperf, I got.. number tabulation practice.  Three runs of each > > > > > test with and without produced nothing but variance/noise. > > > > > > > > Make it go away then. > > > > > > > > If you could write a Changelog for you inspired bit and stick my cleaned > > > > up version under it, I'd be much obliged. > > > > > > Salut, much obliged for eyeball relief. > > > > Unfortunate change log place holder below aside, I think this patch may > > need to be yanked as trading one not readily repeatable regression for > > at least one that definitely is, and likely multiple others. > > > > (adds knob) > > > > Yes, I ws just coming here to reply. I have the results from the first > version of the patch (I don't think the later one fundemtally changed > enough that it will matter but those results are still pending). > > Not entirely surprisingly we've traded a ~10% rand write regression for > 5-10% rand read regression. This makes sense to me since the reads are > more likely to be synchronous and thus be more buddy-like and benefit > from flipping back and forth on the same cpu. OK, so I'm going to make this commit disappear.