Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755242Ab2EBOB2 (ORCPT ); Wed, 2 May 2012 10:01:28 -0400 Received: from e28smtp04.in.ibm.com ([122.248.162.4]:38560 "EHLO e28smtp04.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755211Ab2EBOB0 (ORCPT ); Wed, 2 May 2012 10:01:26 -0400 Date: Wed, 2 May 2012 19:31:17 +0530 From: Srivatsa Vaddagiri To: Peter Zijlstra Cc: Ingo Molnar , Mike Galbraith , Suresh Siddha , Paul Turner , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] sched: steer waking task to empty cfs_rq for better latencies Message-ID: <20120502140117.GC22740@linux.vnet.ibm.com> Reply-To: Srivatsa Vaddagiri References: <20120424165619.GA28701@linux.vnet.ibm.com> <1335286696.28150.206.camel@twins> <1335287354.28150.209.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <1335287354.28150.209.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) x-cbid: 12050214-5564-0000-0000-0000026F70B4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1983 Lines: 46 * Peter Zijlstra [2012-04-24 19:09:14]: > On Tue, 2012-04-24 at 18:58 +0200, Peter Zijlstra wrote: > > 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? > > That is, you're playing a deficiency we should fix, not exploit. > > Also, you do a second loop over all those cpus right after we've already > iterated them.. > > furthermore, that 100%+ gain is still way insane, what else is broken? > Did you try those paravirt tlb-flush patches and other such weirdness? I got around to try pv-tlb-flush patches and it showed >100% improvement for sysbench (without the balance-on-wake patch on host). This was what readprofile showed (when pv-tlb-flush patches were absent in guest): 1135704 total 0.3265 636737 native_cpuid 18192.4857 283201 __bitmap_empty 2832.0100 137853 flush_tlb_others_ipi 569.6405 I will try out how much they help Trade workload (which got me started on this originally) and report back (part of the problem in trying out is that pv-tlb-flush platches are throwing wierd problems - which Nikunj is helping investigate). In any case, we can't expect users to be able to easily upgrade their guest VM kernels and so I am still looking for a solution that works for older guest VM kernels. Paul, hope I can get the global vruntime patches from you soon to test how much it helps! - vatsa -- 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/