From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756624Ab2DXRMk (ORCPT ); Tue, 24 Apr 2012 13:12:40 -0400 Received: from casper.infradead.org ([85.118.1.10]:48541 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755725Ab2DXRMj convert rfc822-to-8bit (ORCPT ); Tue, 24 Apr 2012 13:12:39 -0400 Message-ID: <1335287547.28150.210.camel@twins> Subject: Re: [PATCH v1] sched: steer waking task to empty cfs_rq for better latencies From: Peter Zijlstra To: Srivatsa Vaddagiri Cc: Ingo Molnar , Mike Galbraith , Suresh Siddha , Paul Turner , linux-kernel@vger.kernel.org Date: Tue, 24 Apr 2012 19:12:27 +0200 In-Reply-To: <20120424170743.GA18799@linux.vnet.ibm.com> References: <20120424165619.GA28701@linux.vnet.ibm.com> <1335286696.28150.206.camel@twins> <20120424170743.GA18799@linux.vnet.ibm.com> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2012-04-24 at 22:37 +0530, Srivatsa Vaddagiri wrote: > * Peter Zijlstra [2012-04-24 18:58:16]: > > > On Tue, 2012-04-24 at 22:26 +0530, Srivatsa Vaddagiri wrote: > > > Steer a waking task towards a cpu where its cgroup has zero tasks (in > > > order to provide it better sleeper credits and hence reduce its wakeup > > > latency). > > > > That's just vile.. pjt could you post your global vruntime stuff so > > vatsa can have a go at that? > > The workload I am up against does experience tons of wakeup (after very short > (microsecond range) bursts of sleeps) and so am skeptical how the global > vruntime would keep up with this kind of workload. I'd be happy to test patches > and give feedback! Thing is, global vruntime might fix that flaw/property you're exploiting to get that preemption.