From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: Re: [PATCH v5 6/9] KVM: MMU: introduce pte_prefetch_topup_memory_cache() Date: Tue, 13 Jul 2010 13:48:02 +0800 Message-ID: <4C3BFE12.4060009@cn.fujitsu.com> References: <4C330918.6040709@cn.fujitsu.com> <4C330A37.8080709@cn.fujitsu.com> <4C39C1AB.6000606@redhat.com> <4C3A8694.1000401@cn.fujitsu.com> <4C3B09FD.3060307@redhat.com> <4C3BBE84.30708@cn.fujitsu.com> <4C3BE9BD.40007@redhat.com> <4C3BEAC3.9000501@cn.fujitsu.com> <4C3BFB25.2010602@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM list To: Avi Kivity Return-path: In-Reply-To: <4C3BFB25.2010602@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Avi Kivity wrote: > On 07/13/2010 07:25 AM, Xiao Guangrong wrote: >> >>> Regressions? no. Or do you mean the problem already exists? Where? >>> >> I mean this is a exist problem, likes invlpg, pte-write and sync-page, >> there are >> speculative path that it's not real access, but marked dirty if pte is >> writable. >> > > Right. We should fix those too. > > Prefetch is much more worrying though, especially with ept. If a guest > is using just 1/8 of the pages, it can look to migration as if it's > using 100% of the pages. The impact can be pretty large. We disabled prefetch if ept is enabled since it can break access bit tracking. I'll fix the dirty bit tracking before post the new version of this patchset.