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Thu, 14 Nov 2024 12:07:07 +0100 Message-ID: <95ff75cacab4720bbbecd54e881bb94d97087b45.camel@gmx.de> Subject: Re: [PATCH] sched/fair: Dequeue sched_delayed tasks when waking to a busy CPU From: Mike Galbraith To: Phil Auld Cc: Peter Zijlstra , 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 Date: Thu, 14 Nov 2024 12:07:03 +0100 In-Reply-To: <81de2f710d8922a47364632335ff5ba1a45625b3.camel@gmx.de> References: <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> <0befc9ed8979594d790a8d4fe7ff5c5534c61c3c.camel@gmx.de> <20241112154140.GC336451@pauld.westford.csb> <81de2f710d8922a47364632335ff5ba1a45625b3.camel@gmx.de> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:uYVbsA7vvyAEviHQiubJQBxvNgiOYrhCQ3FxKNuwmUaMTz5gNro saRSPK6cyH9FtDrz72vYE6etAciAPWCgC9xH5EY+jkD/+3Ugpge2PRG6wQ/ARN8PWDmGh3b XVoq0Y4Xh/+budpaOZiPvv7HJoU8w2p48BrcuCV2yW2uCoiRvR7w+Msr9lYO16Yov92NmRv PPO34jk0xzB6hbwoh7ZJA== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:xcYyS/F4+i8=;ua+EqFXQngJA5FaE0xOegFts8uB lDaNY78lMFaSvxBIc45mbga0LRRLsfqOZlwL+cQ0D1LbXcfra1c8Ac8ZxKjMfa67gTfBbZpdZ M+NTjxzDw6Pzi9zWhsXE02CR+/gaii/t4oLZbkDCkhKAvMir6FRrMgwpbSvV6F2WZHfYGo6sO Ghr793dqGCUBP4IlRj4VKz2lckq7c1vEyV1u79Z+DZlcemHAJRDwtBSLtjUguqLDdnzS/sxGS 3geGF/Cui1CLZ4MuaIE+duWj7i9vskbEDoqo+gVWn/UMzoZ6jVpRI+OPIBNmbb7j6bqC4DJk7 beD/PdkCTMNh1Dz1iSJB7bEa5RIbApD2H76XPPPAaR7EEFfz62JGU0JSNtCUlWkQcmkiCZVaa hwecJuo+1r3Yuu7KxxVUiai5OuQ8N5YopjbowPrtOMxlo8ou9ArJJhGiecJ7YGVQqroCGA3Z3 rD9RCDDf/arnLBSo8Zd44JEYz85rMDBmJ6k+TvMKgw+cD52b+CmRTgsN7fR6ofvrxruXqi680 1prumKtmkLibB16YKWIjuFqDgBq0+QByWwbaEglCp74q6CTez8KGiT6XolZY1fpbuJ+JBef8R +WkVY5wJF/b7Evcn6zDsffeF1tpMk8ea3NFlONVcFRth66LFEXUU0iObHDeBELGXt0nFLGMuW PcWXGwswn8XvSCMEsK6xxeGh4Dm+n8zo43qKWQIWOcMlTPlLFq9LSaSQUh0fDGO+Nb/JQmGFJ Z9GJj4z7YVT44xx/4nKCZ6xXvzh9RDwIEv92exIKrlQBlvNPVHQMY77KUfhOjXygF9rzl2VWR 7WLAVYEaRsb9CkiB5rXvrC/a8mtN7D0zfYwt4eskF2/O4VzE908urOJwsKM1fTVbkmStjw5Ri Ic8NSfEQhkpsRpADf3tbEReosLWiKmQT14v102mHXOf2uTHREraxIyqjp On Tue, 2024-11-12 at 17:15 +0100, Mike Galbraith wrote: > On Tue, 2024-11-12 at 10:41 -0500, Phil Auld wrote: > > On Tue, Nov 12, 2024 at 03:23:38PM +0100 Mike Galbraith wrote: > > > > > > > > We don't however have to let sched_delayed block SIS though.=C2=A0 R= endering > > > them transparent in idle_cpu() did NOT wreck the progression, so > > > maaaybe could help your regression. > > > > > > > You mean something like: > > > > if (rq->nr_running > rq->h_nr_delayed) > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return 0; > > > > in idle_cpu() instead of the straight rq->nr_running check? > > Yeah, close enough. The below is all you need. Watching blockage rate during part of a netperf scaling run without, a bit over 2/sec was the highest it got, but with, that drops to the same zero as turning off the feature, so... relevance highly unlikely but not quite impossible? =2D-- kernel/sched/fair.c | 4 ++++ 1 file changed, 4 insertions(+) =2D-- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9454,11 +9454,15 @@ int can_migrate_task(struct task_struct /* * We do not migrate tasks that are: + * 0) not runnable (not useful here/now, but are annoying), or * 1) throttled_lb_pair, or * 2) cannot be migrated to this CPU due to cpus_ptr, or * 3) running (obviously), or * 4) are cache-hot on their current CPU. */ + if (p->se.sched_delayed) + return 0; + if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu)) return 0;