Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759572Ab3DBCZp (ORCPT ); Mon, 1 Apr 2013 22:25:45 -0400 Received: from LGEMRELSE1Q.lge.com ([156.147.1.111]:61043 "EHLO LGEMRELSE1Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758587Ab3DBCZo (ORCPT ); Mon, 1 Apr 2013 22:25:44 -0400 X-AuditID: 9c93016f-b7b6aae000000e9c-c5-515a41a6c8fb Date: Tue, 2 Apr 2013 11:25:56 +0900 From: Joonsoo Kim To: Preeti U Murthy Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, Mike Galbraith , Paul Turner , Alex Shi , Vincent Guittot , Morten Rasmussen , Namhyung Kim Subject: Re: [PATCH 4/5] sched: don't consider upper se in sched_slice() Message-ID: <20130402022556.GD16699@lge.com> References: <1364457537-15114-1-git-send-email-iamjoonsoo.kim@lge.com> <1364457537-15114-5-git-send-email-iamjoonsoo.kim@lge.com> <51553EF5.90702@linux.vnet.ibm.com> <20130401040820.GA12015@lge.com> <5159320C.4050903@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5159320C.4050903@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2384 Lines: 66 Hello, Preeti. On Mon, Apr 01, 2013 at 12:36:52PM +0530, Preeti U Murthy wrote: > Hi Joonsoo, > > On 04/01/2013 09:38 AM, Joonsoo Kim wrote: > > Hello, Preeti. > > > > >> > >> Ideally the children's cpu share must add upto the parent's share. > >> > > > > I don't think so. > > > > We should schedule out the parent tg if 5ms is over. As we do so, we can > > fairly distribute time slice to every tg within short term. If we add > > the children's cpu share upto the parent's, the parent tg may have > > large time slice, so it cannot be preempted easily. There may be a latency > > problem if there are many tgs. > > In the case where the #running < sched_nr_latency, the children's > sched_slices add up to the parent's. > > A rq with two tgs,each with 3 tasks. > > Each of these tasks have a sched slice of > [(sysctl_sched_latency / 3) / 2] as of the present implementation. > > The sum of the above sched_slice of all tasks of a tg will lead to the > sched_slice of its parent: sysctl_sched_latency / 2 > > This breaks when the nr_running on each tg > sched_nr_latency. However I > don't know if this is a good thing or a bad thing. Ah.. Now I get your point. Yes, you are right and it may be good thing. With that property, all tasks in the system can be scheduled at least once in sysctl_sched_latency. sysctl_sched_latency is system-wide configuration, so my patch may be wrong. With my patch, all tasks in the system cannot be scheduled at least once in sysctl_sched_latency. Instead, it schedule all tasks in cfs_rq at least once in sysctl_sched_latency if there is no other tgs. I think that it is real problem that sysctl_sched_min_granularity is not guaranteed for each task. Instead of this patch, how about considering low bound? if (slice < sysctl_sched_min_granularity) slice = sysctl_sched_min_granularity; Thanks. > > Regards > Preeti U Murthy > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/