From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v3 11/11] KVM: MMU: improve write flooding detected Date: Wed, 14 Sep 2011 12:59:01 +0300 Message-ID: <4E707AE5.2030704@redhat.com> References: <4E5C4C20.3000403@cn.fujitsu.com> <4E5C4D17.2080700@cn.fujitsu.com> <4E6F395A.5030609@redhat.com> <4E6FACBD.1020801@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , LKML , KVM To: Xiao Guangrong Return-path: In-Reply-To: <4E6FACBD.1020801@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On 09/13/2011 10:19 PM, Xiao Guangrong wrote: > > > > The spte may not be accessed, but other sptes in the same page can be accessed. An example is the fixmap area for kmap_atomic(), there will be a lot of pte writes but other sptes will be accessed without going through soft-mmu at all. > > I think this kind of shadow pae is mostly the last page table(level=1), maybe > we can skip the write-flooding for the last shadow page, because the last shadow > page can become unsync and it can not let page table write-protected. Yes. > > > I think you have to read the parent_ptes->spte.accessed bits to be sure. > > > > I guess the overload of this way is little high: > - it needs to walk parent ptes for every shadow pages > - we need to clear the parent_ptes->spte.accessed bit when the page is written, and > the tlb flush is needed. > no? > Right. -- error compiling committee.c: too many arguments to function