Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754159AbaGKQMq (ORCPT ); Fri, 11 Jul 2014 12:12:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:18259 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750983AbaGKQMo (ORCPT ); Fri, 11 Jul 2014 12:12:44 -0400 Message-ID: <53C00CC1.1030401@redhat.com> Date: Fri, 11 Jul 2014 12:11:45 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Mike Galbraith CC: Michael wang , Peter Zijlstra , Ingo Molnar , Alex Shi , Paul Turner , Mel Gorman , Daniel Lezcano , LKML Subject: Re: [PATCH] sched: select 'idle' cfs_rq per task-group to prevent tg-internal imbalance References: <53A11A89.5000602@linux.vnet.ibm.com> <20140623094251.GS19860@laptop.programming.kicks-ass.net> <53A8F1DE.2060908@linux.vnet.ibm.com> <20140701082020.GL6758@twins.programming.kicks-ass.net> <53B273A2.5050500@linux.vnet.ibm.com> <53B41B7E.8020009@redhat.com> <1404359462.5137.72.camel@marge.simpson.net> In-Reply-To: <1404359462.5137.72.camel@marge.simpson.net> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 07/02/2014 11:51 PM, Mike Galbraith wrote: > On Wed, 2014-07-02 at 10:47 -0400, Rik van Riel wrote: >> On 07/01/2014 04:38 AM, Michael wang wrote: >>> On 07/01/2014 04:20 PM, Peter Zijlstra wrote: [snip] >>>>> >>>>> Just wondering could we make this another scheduler >>>>> feature? >>>> >>>> No; sched_feat() is for debugging, BIG CLUE: its guarded by >>>> CONFIG_SCHED_DEBUG, anybody using it in production or >>>> anywhere else is broken. >>>> >>>> If people are using it, I should remove or at least randomize >>>> the interface. >>> >>> Fair enough... but is there any suggestions on how to handle >>> this issue? >>> >>> Currently when dbench running with stress, it could only gain >>> one CPU, and cpu-cgroup cpu.shares is meaningless, is there any >>> good methods to address that? >> >> select_idle_sibling will iterate over all of the CPUs in an LLC >> domain if there is no idle cpu in the domain. >> >> I suspect it would not take much extra code to track down the >> idlest CPU in the LLC domain, and make sure to schedule tasks >> there, in case no completely idle CPU was found. >> >> Are there any major problems with that thinking? > > That's full wake balance.. if that was cheap, > select_idle_sibling() would not exist. Full wake balance iterates over all the groups in the system, select_idle_sibling only over one LLC domain. If no CPU in the LLC domain is idle, select_idle_sibling will iterate over all of them. During this iteration, which the code already does, it should be possible to identify the least loaded of the CPUs and pick that one. - -- All rights reversed -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJTwAzBAAoJEM553pKExN6DlrEH/RKQPdAdMFK/pxZ/2f9TCXFK Vq25LWZeJQhNOrH3Q6VzTTfAG06O8+Bjxfb+SR6BOHCtD4kCBqaBdwVVUDXC+MbK NdBa3GtCT3ahvguiYLPEHL1vugND2yzHUgnr9EhUgk6zhnLxfvhIIJj7uv+ZRsri o8DsLrIG1jqDGVbbu5ssZ37w6cldoFBw0FAHcVAquoM2SP+/MuatW1SCkRP31IVL q0dssP1CD0Nkecz+S6WSI59c0Wt0c73oWNg/q41a/kha7RI1J5VF5yNFacq/uL0g Xxyb0mOiJarqMtzuq5ItlOiTry+BpqY1jFhN5ZhFjt9mtvpTR1C/tcXpOw77y0Y= =BEJk -----END PGP SIGNATURE----- -- 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/