From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH 3/6] KVM MMU: optimize/cleanup for marking parent unsync Date: Tue, 13 Apr 2010 12:01:37 -0300 Message-ID: <20100413150137.GB24128@amt.cnet> References: <4BC2D2E2.1030604@cn.fujitsu.com> <4BC2D390.7050708@cn.fujitsu.com> <20100412171211.GC4976@amt.cnet> <4BC3CE83.8020705@cn.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , KVM list , LKML To: Xiao Guangrong Return-path: Content-Disposition: inline In-Reply-To: <4BC3CE83.8020705@cn.fujitsu.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Tue, Apr 13, 2010 at 09:53:07AM +0800, Xiao Guangrong wrote: > > > Marcelo Tosatti wrote: > > > Xiao, > > > > Did you actually see this codepath as being performance sensitive? > > Actually, i not run benchmarks to contrast the performance before this patch > and after this patch. > > > > > I'd prefer to not touch it. > > This patch avoids walk all parents and i think this overload is really unnecessary. > It has other tricks in this codepath but i not noticed? :-) My point is that there is no point in optimizing something unless its performance sensitive. And as i recall, mmu_unsync_walk was much more sensitive performance wise than parent walking. Actually, gfn_to_memslot seems more important since its also noticeable on EPT/NPT hosts.