From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45997) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fVB6G-0000Ag-Lo for qemu-devel@nongnu.org; Tue, 19 Jun 2018 03:30:49 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fVB6D-0005VX-Hq for qemu-devel@nongnu.org; Tue, 19 Jun 2018 03:30:48 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:36524 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fVB6D-0005VI-CJ for qemu-devel@nongnu.org; Tue, 19 Jun 2018 03:30:45 -0400 Date: Tue, 19 Jun 2018 15:30:34 +0800 From: Peter Xu Message-ID: <20180619073034.GA14814@xz-mi> References: <20180604095520.8563-1-xiaoguangrong@tencent.com> <20180604095520.8563-7-xiaoguangrong@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180604095520.8563-7-xiaoguangrong@tencent.com> Subject: Re: [Qemu-devel] [PATCH 06/12] migration: do not detect zero page for compression List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: guangrong.xiao@gmail.com Cc: pbonzini@redhat.com, mst@redhat.com, mtosatti@redhat.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, dgilbert@redhat.com, jiang.biao2@zte.com.cn, wei.w.wang@intel.com, Xiao Guangrong On Mon, Jun 04, 2018 at 05:55:14PM +0800, guangrong.xiao@gmail.com wrote: > From: Xiao Guangrong > > Detecting zero page is not a light work, we can disable it > for compression that can handle all zero data very well Is there any number shows how the compression algo performs better than the zero-detect algo? Asked since AFAIU buffer_is_zero() might be fast, depending on how init_accel() is done in util/bufferiszero.c. >>From compression rate POV of course zero page algo wins since it contains no data (but only a flag). Regards, -- Peter Xu