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[31.46.243.213]) by smtp.gmail.com with ESMTPSA id m25-20020a17090607d900b009883a3edcfcsm4620183ejc.171.2023.06.22.05.01.10 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Jun 2023 05:01:11 -0700 (PDT) Sender: Ingo Molnar Date: Thu, 22 Jun 2023 14:01:07 +0200 From: Ingo Molnar To: Joel Fernandes Cc: Peter Zijlstra , vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, corbet@lwn.net, qyousef@layalina.io, chris.hyser@oracle.com, patrick.bellasi@matbug.net, pjt@google.com, pavel@ucw.cz, qperret@google.com, tim.c.chen@linux.intel.com, joshdon@google.com, timj@gnu.org, kprateek.nayak@amd.com, yu.c.chen@intel.com, youssefesmat@chromium.org, efault@gmx.de, tglx@linutronix.de Subject: Re: [PATCH 08/15] sched: Commit to EEVDF Message-ID: References: <20230531115839.089944915@infradead.org> <20230531124604.137187212@infradead.org> <20230616212353.GA628850@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230616212353.GA628850@google.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Joel Fernandes wrote: > On Wed, May 31, 2023 at 01:58:47PM +0200, Peter Zijlstra wrote: > > EEVDF is a better defined scheduling policy, as a result it has less > > heuristics/tunables. There is no compelling reason to keep CFS around. > > > > Signed-off-by: Peter Zijlstra (Intel) > > --- > > kernel/sched/debug.c | 6 > > kernel/sched/fair.c | 465 +++--------------------------------------------- > > Whether EEVDF helps us improve our CFS latency issues or not, I do like the > merits of this diffstat alone and the lesser complexity and getting rid of > those horrible knobs is kinda nice. To to be fair, the "removal" in this patch is in significant part an artifact of the patch series itself, because first EEVDF bits get added by three earlier patches, in parallel to CFS: kernel/sched/fair.c | 137 +++++++++++++++++++++++++++++++++++++++++++++++++-- kernel/sched/fair.c | 162 +++++++++++++++++++++++++++++++++++++----------- kernel/sched/fair.c | 338 +++++++++++++++++++++++++++++++++++++++++------- ... and then we remove the old CFS policy code in this 'commit to EEVDF' patch: kernel/sched/fair.c | 465 +++--------------------------------------------- The combined diffstat is close to 50% / 50% balanced: kernel/sched/fair.c | 1105 ++++++++++++++++++-------------------- But having said that, I do agree that EEVDF as submitted by Peter is better defined, with fewer heuristics, which is an overall win - so no complaints from me! Thanks, Ingo