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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82C03ECAAD3 for ; Mon, 19 Sep 2022 11:57:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229838AbiISL46 (ORCPT ); Mon, 19 Sep 2022 07:56:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46288 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230198AbiISL4F (ORCPT ); Mon, 19 Sep 2022 07:56:05 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1DA112DAA2 for ; Mon, 19 Sep 2022 04:55:37 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 88F231474; Mon, 19 Sep 2022 04:55:42 -0700 (PDT) Received: from [192.168.178.82] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 106293F73B; Mon, 19 Sep 2022 04:55:32 -0700 (PDT) Message-ID: <000c2893-feb4-373d-2234-2ca74be94714@arm.com> Date: Mon, 19 Sep 2022 13:55:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v4 6/8] sched/fair: Add sched group latency support Content-Language: en-US To: Vincent Guittot , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, linux-kernel@vger.kernel.org, parth@linux.ibm.com Cc: qais.yousef@arm.com, chris.hyser@oracle.com, valentin.schneider@arm.com, patrick.bellasi@matbug.net, David.Laight@aculab.com, pjt@google.com, pavel@ucw.cz, tj@kernel.org, qperret@google.com, tim.c.chen@linux.intel.com, joshdon@google.com References: <20220916080305.29574-1-vincent.guittot@linaro.org> <20220916080305.29574-7-vincent.guittot@linaro.org> From: Dietmar Eggemann In-Reply-To: <20220916080305.29574-7-vincent.guittot@linaro.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org s/valentin.schneider@arm.com// On 16/09/2022 10:03, Vincent Guittot wrote: > Task can set its latency priority, which is then used to decide to preempt > the current running entity of the cfs, but sched group entities still have > the default latency offset. > > Add a latency field in task group to set the latency offset of the > sched_eneities of the group, which will be used against other entities in s/sched_eneities/sched_entity > the parent cfs when deciding which entity to schedule first. So latency for cgroups does not follow any (existing) Resource Distribution Model/Scheme (Documentation/admin-guide/cgroup-v2.rst)? Latency values are only used to compare sched entities at the same level. [...] > +static int cpu_latency_write_s64(struct cgroup_subsys_state *css, > + struct cftype *cft, s64 latency) > +{ There is no [MIN, MAX] checking? min_weight = sched_latency_to_weight[0] = -1024 max_weight = sched_latency_to_weight[39] = 973 [MIN, MAX] = [sysctl_sched_latency * min_weight >> NICE_LATENCY_SHIFT, sysctl_sched_latency * max_weight >> NICE_LATENCY_SHIFT] With the `cpu.latency` knob user would have to know for example that the value is -24,000,000ns to get the same behaviour as for a task latency nice = -20 (latency prio = 0) (w/ sysctl_sched_latency = 24ms)? For `nice` we have `cpu.weight.nice` next to `cpu.weight` in cgroup v2 ? [...]