From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8D4ACC433FF for ; Wed, 31 Jul 2019 17:32:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6DCCC20679 for ; Wed, 31 Jul 2019 17:32:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730846AbfGaRcc (ORCPT ); Wed, 31 Jul 2019 13:32:32 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:45086 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728943AbfGaRc2 (ORCPT ); Wed, 31 Jul 2019 13:32:28 -0400 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 512) id BCF558031F; Wed, 31 Jul 2019 19:32:14 +0200 (CEST) Date: Wed, 31 Jul 2019 19:32:26 +0200 From: Pavel Machek To: Parth Shah Cc: peterz@infradead.org, mingo@redhat.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, patrick.bellasi@arm.com, dietmar.eggemann@arm.com, daniel.lezcano@linaro.org, subhra.mazumdar@oracle.com Subject: Re: [RFC v4 0/8] TurboSched: A scheduler for sustaining Turbo Frequencies for longer durations Message-ID: <20190731173225.GB24222@amd> References: <20190725070857.6639-1-parth@linux.ibm.com> <20190728133102.GD8718@xo-6d-61-c0.localdomain> <4fcd3488-6ba0-bc22-a08d-ceebbce1c120@linux.ibm.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="IrhDeMKUP4DT/M7F" Content-Disposition: inline In-Reply-To: <4fcd3488-6ba0-bc22-a08d-ceebbce1c120@linux.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --IrhDeMKUP4DT/M7F Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > >> Abstract > >> =3D=3D=3D=3D=3D=3D=3D=3D > >> > >> The modern servers allows multiple cores to run at range of frequencies > >> higher than rated range of frequencies. But the power budget of the sy= stem > >> inhibits sustaining these higher frequencies for longer durations. > >=20 > > Thermal budget? >=20 > Right, it is a good point, and there can be possibility of Thermal thrott= ling > which is not covered here. > But the thermal throttling is less often seen in the servers than the thr= ottling > due to the Power budget constraints. Also one can change the power cap wh= ich leads > to increase in the throttling and task packing can handle in such > cases. Ok. I thought you are doing this due to thermals. If I understand things correctly, you can go over thermal limits for a few seconds before the silicon heats up. What is the timescale for power budget? > BTW, Task packing allows few more cores to remain idle for longer time, so > shouldn't this decrease thermal throttles upto certain extent? I guess so, yes. > > >> These numbers are w.r.t. `turbo_bench.c` multi-threaded test benchma= rk > >> which can create two kinds of tasks: CPU bound (High Utilization) and > >> Jitters (Low Utilization). N in X-axis represents N-CPU bound and N-Ji= tter > >> tasks spawned. > >=20 > > Ok, so you have description how it causes 13% improvements. Do you also= have metrics how > > it harms performance.. how much delay is added to unimportant tasks etc= =2E..? > >=20 >=20 > Yes, if we try to pack the tasks despite of no frequency throttling, we s= ee a regression > around 5%. For instance, in the synthetic benchmark I used to show perfor= mance benefit, > for lower count of CPU intensive threads (N=3D2) there is -5% performance= drop. >=20 > Talking about the delay added to an unimportant tasks, the result can be = lower throughput > or higher latency for such tasks. Thanks. I believe it would be good to mention disadvantages in the documentation, too. Best regards, Pavel =09 --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --IrhDeMKUP4DT/M7F Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAl1B0KkACgkQMOfwapXb+vK/SQCdEakOOhPJoZSXw6d1ALOX3ZWx knYAn2U5kHCHmxOCvozd/2HU6N2RxX4Z =4uGg -----END PGP SIGNATURE----- --IrhDeMKUP4DT/M7F--