From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takuya Yoshikawa Date: Tue, 17 Apr 2012 12:37:48 +0000 Subject: Re: [PATCH 00/13] KVM: MMU: fast page fault Message-Id: <20120417213748.f3c4ae8d0056676fd33a47c5@gmail.com> List-Id: References: <4F742951.7080003@linux.vnet.ibm.com> <4F82E04E.6000900@redhat.com> <20120409175829.GB21894@amt.cnet> <4F8329D3.7000605@gmail.com> <20120409194614.GB23053@amt.cnet> <4F840DD2.3090101@redhat.com> <20120410204031.ffb5b976225ac9fe6dae474e@gmail.com> <4F842074.1050108@linux.vnet.ibm.com> <20120411211514.35db29c11460516e604059b6@gmail.com> <4F857B61.9080602@linux.vnet.ibm.com> <20120411231441.9d0984672dd252b806f99128@gmail.com> <20120413232528.c5ddbddb3cc0870d6e85a332@gmail.com> <4F8A95CB.9070104@redhat.com> <20120417004935.a9a39d951b3c24588e29edd2@gmail.com> <4F8D0D29.9050009@linux.vnet.ibm.com> <4F8D210C.8070505@redhat.com> In-Reply-To: <4F8D210C.8070505@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Avi Kivity Cc: Xiao Guangrong , kvm-ppc@vger.kernel.org, Marcelo Tosatti , Xiao Guangrong , LKML , KVM On Tue, 17 Apr 2012 10:51:40 +0300 Avi Kivity wrote: > That's true with the write protect everything approach we use now. But > it's not true with range-based write protection, where you issue > GET_DIRTY_LOG on a range of pages and only need to re-write-protect them. > > (the motivation for that is to decrease the time between GET_DIRTY_LOG > and sending the page; as the time increases, the chances that the page > got re-dirtied go up). Thank you for explaining this. I was planning to give the userspace more freedom. Since there are many known algorithms to predict hot memory pages, the userspace will be able to tune the frequency of GET_DIRTY_LOG for such parts not to get too many faults repeatedly, if we can restrict the range of pages to protect. This is the fine-grained control. Thanks, Takuya