From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932404Ab0JAL7n (ORCPT ); Fri, 1 Oct 2010 07:59:43 -0400 Received: from casper.infradead.org ([85.118.1.10]:49324 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932374Ab0JAL7f convert rfc822-to-8bit (ORCPT ); Fri, 1 Oct 2010 07:59:35 -0400 Subject: Re: [PATCH 1/2] sched: normalize sleeper's vruntime during group change From: Peter Zijlstra To: Dima Zavin Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Mike Galbraith , Arve =?ISO-8859-1?Q?Hj=F8nnev=E5g?= In-Reply-To: References: <1285742774-5013-1-git-send-email-dima@android.com> <1285843669.2144.2.camel@laptop> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Fri, 01 Oct 2010 13:59:28 +0200 Message-ID: <1285934368.2144.60.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2010-09-30 at 12:14 -0700, Dima Zavin wrote: > > > Please explain this stuff.. > > The situation today is quite bad for sleeping tasks. Currently, when > you move a sleeping thread between cgroups, the thread can retain its > old vruntime value if the old group was far ahead of the new group > since it essentially does a max(se->vruntime, new_vruntime) in > place_entity. This can prevent the task from running for a very long > time. That is what this patch was trying to address. It normalizes the > sleeper thread's vruntime before moving it to the new group. > > Hrm,.. ok, I tend to not use this cgroup gunk more that I absolutely have to, so I'll take your word for it. But doesn't normal cross-cpu task migration already solve this problem? Therefore wouldn't it be possible to adapt/extend that code to also deal with this particular issue? It would avoid growing more cgroup fudge..