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Tue, 11 Apr 2023 16:56:26 +0200 Message-ID: <584da7e2052a11f432afaf623e567610ce17c78b.camel@gmx.de> Subject: Re: [PATCH 00/17] sched: EEVDF using latency-nice From: Mike Galbraith To: Hillf Danton Cc: Peter Zijlstra , mingo@kernel.org, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mgorman@suse.de, bristot@redhat.com, corbet@lwn.net, kprateek.nayak@amd.com, youssefesmat@chromium.org, joel@joelfernandes.org Date: Tue, 11 Apr 2023 16:56:24 +0200 In-Reply-To: <20230411133333.1790-1-hdanton@sina.com> References: <20230328092622.062917921@infradead.org> <20230410082307.1327-1-hdanton@sina.com> <20230411133333.1790-1-hdanton@sina.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:LZ4LcL2xRWvnRFA4Rg8812btaqUC/LgLwUeUiZGpvZWv9QZmzBx w8Qn+DNLgm1iGjdcvVjmo0tR5uhfRaFK39gxeg9Dr9ftgokR8ItPlxyL8p+hSMywuj23zaI xbxeGQt9IzOmhRjQ5Qu6mViUlpYflKZY13a/g1J6mWVPpqVsu/EAWKfmwvs/R69lhhObehl 6ylr53eioCD4QFaVrRv6A== UI-OutboundReport: notjunk:1;M01:P0:ozvJc9Xwgc0=;yXLb0mfuEsFNRb2/+mU5kJrKgfA kdCqD8sUCTswrtyrBBuzO6yBsvQgHvT3qOE1wYQe1jWDE7s8UuVbHaorF376zWwRuBt7Ve7SR acAs1xIIrdZ7DVaEDCwQKeSpW/UenoTe4F4RgzUewiRNhClhsV/f88kw8tid+fL7Yc3xDKF1p BEsBHeqPCK4IgKRtXA5wE35vFeu59vYUCEzg2mUr1BBi16olL7peTS64IPi/6VCyu4To6rYcu 7YGJTYxtikO13fDYSE8QmIf3+kTclwqAdIo6uKi6/xstqy0vhlO4YcTGSYUXtWhH8lizRtt9V Jr9+W271IXzct1YHJSLk+rs9GZE7oMKR5hWQHRvMAW2a7gsiG9+jVa5J1JG+0MXRfRtx8dsbO GD7+bFfVdqXrpp/ALikaxYc6JX+GrbuuCqqu8xApL21Om2ekxHe93pgIO9d9ZireIFxXBPCLz fh4Qc8/t2vdrk0JLRhU7i/Ce1lFlPKoe+hzs0HuOyTjG6xaKIIIQYa4SdPT/PHCjybS2GvpZn qexKyV0E2KpMYTsAbmL+tC9z1Qq0cVmk1vX9aES9jrSnM82ZbzdK6lR185rCkkxjoOfh8RZg5 2s6tjkss9zsETm+KmhCyZ5B8BHASVoxij5epEDWbMZZI9xzt02f8ShQ6aJ7Fr17wUQBVS9Ny0 x+fZFAx/IgUeSlIb/e4Cd5w6aaiiK2/Vhh9y6CNqL10+XdOSzp1ux9lRQwXLUsZYubtoEzDuo Hl/sDzdeFqYsfI4c9waFwaNRYPgN4WSyhLqNkhzFecBVkvPhQjSJehpM8dCBqllZQtSGAux2T b1l8ldT+omc2aGkCFVOblb4d+CmBAZ2V/5l7iuVD9Pkj4HpYPZZ7S/EditBQnBGBTfqVYSoAs fA0RUCvCZonqdRv8b+O6RO4L50ArdIzuV+NEaUNoXOopAr5w+NHCMD8rrl37H0KAaf+DOM5rs 8qwu9iPg5Ad2RxIpNJwPfR/Yr80= X-Stat-Signature: 7rh1r1gahdsqij6ayt4yhns1mxikirb8 X-Rspam-User: X-Rspamd-Queue-Id: 977A040012 X-Rspamd-Server: rspam06 X-HE-Tag: 1681224997-663802 X-HE-Meta: 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 XgFZ6dBd HWvgKtsuBl6lwWyJyy/A/AxkYgnIvM2+4McAL9YDMy1UDLwF0cLrf1rp4fQKYj8iTgVceYcdAuBCEgq+yw7qmyZLSwaJkhJZyiqNK+EY7Gfm1eAoQXAzRjxeqYtaLE4p8tOnEaatiy7EAvcoezkqQQ00N5n1fuWQhhTeJrOlNq6v/O3gZkbHgbaFgR6vtyroyo159f7NEtPKwhXrvq3n99YPaPfIbNbhJeZhJxc0TTuhdkIkoZbMSCRRTvaPd3K2DjCorU8FhTFn98CUIB09W9Ffk+TSClFxFJ6nNK3hTsToHMV6IjE2yg90jBm4/j6qKlR+az9RoZ+vOPBs= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 2023-04-11 at 21:33 +0800, Hillf Danton wrote: > On Tue, 11 Apr 2023 12:15:41 +0200 Mike Galbraith > > > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -950,6 +950,9 @@ static struct sched_entity *pick_eevdf(s > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (curr && (!curr->on= _rq || !entity_eligible(cfs_rq, curr))) > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0curr =3D3D NULL; > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0if (sched_feat(GENTLE_EEVDF= ) && curr) > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0return curr; > > + > > This is rather aggressive, given latency-10 curr and latency-0 candidate > at tick hit for instance. The numbers seem to indicate that the ~400k ctx switches eliminated were meaningless to the load being measures. I recorded everything for 5 minutes, and the recording wide max actually went down.. but one-off hits happen regularly in noisy GUI regardless of scheduler, are difficult to assign meaning to. Now I'm not saying there is no cost, if you change anything that's converted to instructions, there is a price tag somewhere, whether you notice immediately or not. Nor am I saying that patchlet is golden. I am saying that some of the ctx switch delta look very much like useless overhead that can and should be made to go away. From my POV, patchlet actually looks like kinda viable, but to Peter and regression reporter, it and associated data are presented as a datapoint. > And along your direction a mild change is > postpone the preempt wakeup to the next tick. > > +++ b/kernel/sched/fair.c > @@ -7932,8 +7932,6 @@ static void check_preempt_wakeup(struct > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0return; > =C2=A0 > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0cfs_rq =3D cfs_rq_of(se)= ; > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0update_curr(cfs_rq); > - > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0/* > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 * XXX pick_eevdf(cfs_rq= ) !=3D se ? > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */ Mmmm, stopping time is a bad idea methinks. -Mike