From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752056AbeEAHLU (ORCPT ); Tue, 1 May 2018 03:11:20 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:36216 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751340AbeEAHLT (ORCPT ); Tue, 1 May 2018 03:11:19 -0400 Date: Tue, 1 May 2018 09:11:12 +0200 From: Peter Zijlstra To: Cong Wang Cc: LKML , Paul Turner , Mike Galbraith , Thomas Gleixner , Ingo Molnar Subject: Re: [PATCH] sched/fair: make CFS bandwidth slice per cpu group Message-ID: <20180501071112.GD12217@hirez.programming.kicks-ass.net> References: <20180430192925.12589-1-xiyou.wangcong@gmail.com> <20180430194251.GB12217@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 30, 2018 at 01:37:16PM -0700, Cong Wang wrote: > On Mon, Apr 30, 2018 at 12:42 PM, Peter Zijlstra wrote: > > On Mon, Apr 30, 2018 at 12:29:25PM -0700, Cong Wang wrote: > >> Currently, the sched_cfs_bandwidth_slice_us is a global setting which > >> affects all cgroups. Different groups may want different values based > >> on their own workload, one size doesn't fit all. The global pool filled > >> periodically is per cgroup too, they should have the right to distribute > >> their own quota to each local CPU with their own frequency. > > > > Why.. what happens? This doesn't really tell us anything. > > We saw tasks in a container got throttled for many times even > when they don't apparently over-burn the CPU's. I tried to reduce > the sched_cfs_bandwidth_slice_us from the default 5ms to 1ms, > it solved the problem as no tasks got throttled after this change. > This is why I want to change it. The 1ms slice distributes time better at the cost of higher overhead, right? > And I don't think 1ms will be good for all containers, so in order to > minimize the impact, I would like to keep the slice change within > each container. This is why I propose this patch rather just > `sysctl -w`. Do you think otherwise? Well, I think I don't quite remember everything and a Changelog that tells me why you want stuff in a little more detail and helps me remember some things is a lot more useful than me having to go dig through the code myself (which I'll invariably postpone because I'm a busy sort of person). > BTW, people reported a similar (if not same) issue here before: > https://gist.github.com/bobrik/2030ff040fad360327a5fab7a09c4ff1 That's not a report, that's a random person on the interweb posting random crap. A report lands in my inbox.