From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nikunj A Dadhania Subject: Re: [PATCH v4 0/8] KVM paravirt remote flush tlb Date: Tue, 04 Sep 2012 13:38:06 +0530 Message-ID: <87ligqdxcp.fsf@abhimanyu.in.ibm.com> References: <20120821112346.3512.99814.stgit@abhimanyu.in.ibm.com> <5044BFCA.7060303@redhat.com> <87txveefrc.fsf@abhimanyu.in.ibm.com> <5045B2EA.2030301@redhat.com> Mime-Version: 1.0 Content-Type: text/plain Cc: mtosatti@redhat.com, raghukt@linux.vnet.ibm.com, alex.shi@intel.com, kvm@vger.kernel.org, stefano.stabellini@eu.citrix.com, peterz@infradead.org, hpa@zytor.com, vsrivatsa@gmail.com, mingo@elte.hu To: Avi Kivity Return-path: Received: from e23smtp09.au.ibm.com ([202.81.31.142]:51912 "EHLO e23smtp09.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751544Ab2IDIIu (ORCPT ); Tue, 4 Sep 2012 04:08:50 -0400 Received: from /spool/local by e23smtp09.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 4 Sep 2012 18:07:14 +1000 Received: from d23av02.au.ibm.com (d23av02.au.ibm.com [9.190.235.138]) by d23relay05.au.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q847xbiR24510628 for ; Tue, 4 Sep 2012 17:59:38 +1000 Received: from d23av02.au.ibm.com (loopback [127.0.0.1]) by d23av02.au.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q8488g3G017622 for ; Tue, 4 Sep 2012 18:08:44 +1000 In-Reply-To: <5045B2EA.2030301@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, 04 Sep 2012 10:51:06 +0300, Avi Kivity wrote: > On 09/04/2012 04:30 AM, Nikunj A Dadhania wrote: > > On Mon, 03 Sep 2012 17:33:46 +0300, Avi Kivity wrote: > >> On 08/21/2012 02:25 PM, Nikunj A. Dadhania wrote: > >> > > >> > kernbench(lower is better) > >> > ========================== > >> > base pvflushv4 %improvement > >> > 1VM 48.5800 46.8513 3.55846 > >> > 2VM 108.1823 104.6410 3.27346 > >> > 3VM 183.2733 163.3547 10.86825 > >> > > >> > ebizzy(higher is better) > >> > ======================== > >> > base pvflushv4 %improvement > >> > 1VM 2414.5000 2089.8750 -13.44481 > >> > 2VM 2167.6250 2371.7500 9.41699 > >> > 3VM 1600.1111 2102.5556 31.40060 > >> > > >> > >> The regression is worrying. We're improving the contended case at the > >> cost of the non-contended case, this is usually the wrong thing to do. > >> Do we have any clear idea of the cause of the regression? > >> > > Previous perf numbers suggest that in 1VM scenario flush_tlb_others_ipi > > is around 2%, while for contented case its around 10%. That is what is > > helping contended case. > > But what is causing the regression for the uncontended case? > Haven't been able to nail that, any clue on how to profile would help. Regards Nikunj