Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753918Ab1F2MTF (ORCPT ); Wed, 29 Jun 2011 08:19:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:29846 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751123Ab1F2MS7 (ORCPT ); Wed, 29 Jun 2011 08:18:59 -0400 Message-ID: <4E0B182C.1090402@redhat.com> Date: Wed, 29 Jun 2011 15:18:52 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10 MIME-Version: 1.0 To: Xiao Guangrong CC: Marcelo Tosatti , LKML , KVM Subject: Re: [PATCH v2 19/22] KVM: MMU: lockless walking shadow page table References: <4E01FBC9.3020009@cn.fujitsu.com> <4E01FDB4.60306@cn.fujitsu.com> <4E0AED86.2060908@redhat.com> <4E0B0997.4090206@cn.fujitsu.com> <4E0B09EA.1040304@redhat.com> <4E0B1191.6040100@cn.fujitsu.com> In-Reply-To: <4E0B1191.6040100@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1284 Lines: 30 On 06/29/2011 02:50 PM, Xiao Guangrong wrote: > >> > > >> > I think we should do this unconditionally. The cost of ping-ponging the shared cache line containing reader_counter will increase with large smp counts. On the other hand, zap_page is very rare, so it can be a little slower. Also, less code paths = easier to understand. > >> > > >> > >> On soft mmu, zap_page is very frequently, it can cause performance regression in my test. > > > > Any idea what the cause of the regression is? It seems to me that simply deferring freeing shouldn't have a large impact. > > > > I guess it is because the page is freed too frequently, i have done the test, it shows > about 3219 pages is freed per second > > Kernbench performance comparing: > > the origin way: 3m27.723 > free all shadow page in rcu context: 3m30.519 I don't recall seeing such a high free rate. Who is doing all this zapping? You may be able to find out with the function tracer + call graph. -- error compiling committee.c: too many arguments to function -- 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/