From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751968AbbGMMan (ORCPT ); Mon, 13 Jul 2015 08:30:43 -0400 Received: from mail-wg0-f50.google.com ([74.125.82.50]:33674 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751887AbbGMMal (ORCPT ); Mon, 13 Jul 2015 08:30:41 -0400 Message-ID: <1436790638.6576.190.camel@gmail.com> Subject: Re: [PATCH v2] sched: let __sched_period() use rq's nr_running From: Mike Galbraith To: Byungchul Park Cc: Morten Rasmussen , mingo@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org Date: Mon, 13 Jul 2015 14:30:38 +0200 In-Reply-To: <20150713110746.GK31287@byungchulpark-X58A-UD3R> References: <1436515890-10792-1-git-send-email-byungchul.park@lge.com> <20150710133107.GC8668@e105550-lin.cambridge.arm.com> <20150713005639.GH31287@byungchulpark-X58A-UD3R> <1436771221.6576.60.camel@gmail.com> <20150713082900.GI31287@byungchulpark-X58A-UD3R> <1436782937.6576.103.camel@gmail.com> <20150713110746.GK31287@byungchulpark-X58A-UD3R> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2015-07-13 at 20:07 +0900, Byungchul Park wrote: > i still think stretching with local cfs's nr_running should be replaced with > stretching with a top(=root) level one. I think we just can't take 'slice' _too_ seriously. Not only is it annoying with cgroups, the scheduler simply doesn't deliver 'slices' in the traditional sense, it equalizes vruntimes, planning to do that at slice granularity. FAIR_SLEEPERS doesn't make that planning any easier. With a pure compute load and no HR_TICK, what you get is tick granularity preemption checkpoints, but having just chewed up a 'slice' means nothing if you're still leftmost. It's all about vruntime, so leftmost can have back to back 'slices'. FAIR_SLEEPERS just increases the odds that leftmost WILL take more than one 'slice'. (we could perhaps decay deficit after a full slice or such to decrease the spread growth that sleepers induce. annoying problem, especially so with a gaggle of identical sleepers, as sleep time becomes meaningless, there is no differential to equalize.. other than the ones we create.. but I'm digressing, a lot, time to stop thinking/typing, go do work;) -Mike