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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 798BDC7618B for ; Sun, 28 Jul 2019 13:31:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 58E462077C for ; Sun, 28 Jul 2019 13:31:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726046AbfG1NbJ (ORCPT ); Sun, 28 Jul 2019 09:31:09 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:59088 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726032AbfG1NbJ (ORCPT ); Sun, 28 Jul 2019 09:31:09 -0400 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 512) id D830B8021E; Sun, 28 Jul 2019 15:30:55 +0200 (CEST) Date: Sun, 28 Jul 2019 15:31:02 +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: <20190728133102.GD8718@xo-6d-61-c0.localdomain> References: <20190725070857.6639-1-parth@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190725070857.6639-1-parth@linux.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Hi! > Abstract > ======== > > The modern servers allows multiple cores to run at range of frequencies > higher than rated range of frequencies. But the power budget of the system > inhibits sustaining these higher frequencies for longer durations. Thermal budget? Should this go to documentation somewhere? > Current CFS algorithm in kernel scheduler is performance oriented and hence > tries to assign any idle CPU first for the waking up of new tasks. This > policy is perfect for major categories of the workload, but for jitter > tasks, one can save energy by packing them onto the active cores and allow > those cores to run at higher frequencies. > > These patch-set tunes the task wake up logic in scheduler to pack > exclusively classified jitter tasks onto busy cores. The work involves the > jitter tasks classifications by using syscall based mechanisms. > > In brief, if we can pack jitter tasks on busy cores then we can save power > by keeping other cores idle and allow busier cores to run at turbo > frequencies, patch-set tries to meet this solution in simplest manner. > Though, there are some challenges in implementing it(like smt_capacity, Space before (. > These numbers are w.r.t. `turbo_bench.c` multi-threaded test benchmark > 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-Jitter > tasks spawned. 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...? Thanks, Pavel