Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754359Ab3EHLg1 (ORCPT ); Wed, 8 May 2013 07:36:27 -0400 Received: from merlin.infradead.org ([205.233.59.134]:59267 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752317Ab3EHLg0 (ORCPT ); Wed, 8 May 2013 07:36:26 -0400 Date: Wed, 8 May 2013 13:34:42 +0200 From: Peter Zijlstra To: Paul Turner Cc: Alex Shi , Morten Rasmussen , Ingo Molnar , Thomas Gleixner , Andrew Morton , Borislav Petkov , Namhyung Kim , Mike Galbraith , Vincent Guittot , Preeti U Murthy , Viresh Kumar , LKML , Mel Gorman , Rik van Riel , Michael Wang Subject: Re: [PATCH v5 3/7] sched: set initial value of runnable avg for new forked task Message-ID: <20130508113442.GB6803@dyad.programming.kicks-ass.net> References: <1367804711-30308-1-git-send-email-alex.shi@intel.com> <1367804711-30308-4-git-send-email-alex.shi@intel.com> <5187760D.8060900@intel.com> <51886460.3020009@intel.com> <20130507095715.GE4068@e103034-lin> <5188DFEF.6010403@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1538 Lines: 33 On Tue, May 07, 2013 at 04:20:55AM -0700, Paul Turner wrote: > Yes, 1024 was only intended as a starting point. We could also > arbitrarily pick something larger, the key is that we pick > _something_. > > If we wanted to be more exacting about it we could just give them a > sched_slice() worth; this would have a few obvious "nice" properties > (pun intended). Oh I see I misunderstood again :/ Its not about the effective load but weight of the initial effective load wrt adjustment. Previous schedulers didn't have this aspect at all, so no experience from me here. Paul would be the one, since he's ran longest with this stuff. That said, I would tend to keep it shorter rather than longer so that it would adjust quicker to whatever it really wanted to be. Morten says the load is unstable specifically on loaded systems. I would think this is because we'd experience scheduling latency, we're runnable more pushing things up. But if we're really an idle task at heart we'd not run again for a long while, pushing things down again. So on that point Paul's suggestion of maybe starting with __sched_slice() might make sense because it increases the weight of the initial avg with nr_running. Not sure really, we'll have to play and see what works best for a number of workloads. -- 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/