From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753209Ab1L0JRv (ORCPT ); Tue, 27 Dec 2011 04:17:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51253 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752662Ab1L0JRr (ORCPT ); Tue, 27 Dec 2011 04:17:47 -0500 Message-ID: <4EF98D29.1080809@redhat.com> Date: Tue, 27 Dec 2011 11:17:29 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111115 Thunderbird/8.0 MIME-Version: 1.0 To: Nikunj A Dadhania CC: Ingo Molnar , peterz@infradead.org, linux-kernel@vger.kernel.org, vatsa@linux.vnet.ibm.com, bharata@linux.vnet.ibm.com Subject: Re: [RFC PATCH 0/4] Gang scheduling in CFS References: <20111219083141.32311.9429.stgit@abhimanyu.in.ibm.com> <20111219112326.GA15090@elte.hu> <87sjke1a53.fsf@abhimanyu.in.ibm.com> <4EF1B85F.7060105@redhat.com> <877h1o9dp7.fsf@linux.vnet.ibm.com> <20111223103620.GD4749@elte.hu> <4EF701C7.9080907@redhat.com> <87vcp4t45p.fsf@linux.vnet.ibm.com> <877h1iu2md.fsf@linux.vnet.ibm.com> In-Reply-To: <877h1iu2md.fsf@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/27/2011 05:15 AM, Nikunj A Dadhania wrote: > On Mon, 26 Dec 2011 08:44:58 +0530, Nikunj A Dadhania wrote: > > On Sun, 25 Dec 2011 12:58:15 +0200, Avi Kivity wrote: > > > On 12/23/2011 12:36 PM, Ingo Molnar wrote: > > > > * Nikunj A Dadhania wrote: > > > > > > [...] > > > > > > > > > > I see the main difference between both the reports is: > > > > > native_flush_tlb_others. > > > > > > > > So it would be important to figure out why ebizzy gets into so > > > > many TLB flushes and why gang scheduling makes it go away. > > > > > > The second part is easy - a remote tlb flush involves IPIs to many other > > > vcpus (possible waking them up and scheduling them), then busy-waiting > > > until they acknowledge the flush. Gang scheduling is really good here > > > since it shortens the busy wait, would be even better if we schedule > > > halted vcpus (see the yield_on_hlt module parameter, set to 0). > > I will check this. > > > I am seeing a drop of ~44% when setting yield_on_hlt = 0 > A drop of 44% of what? -- error compiling committee.c: too many arguments to function