From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51835) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e9pap-0000zu-U5 for qemu-devel@nongnu.org; Wed, 01 Nov 2017 05:45:56 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e9pai-0007wy-04 for qemu-devel@nongnu.org; Wed, 01 Nov 2017 05:45:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43738) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e9pah-0007vU-LP for qemu-devel@nongnu.org; Wed, 01 Nov 2017 05:45:43 -0400 Date: Wed, 1 Nov 2017 09:45:38 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20171101094537.GA2786@work-vm> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] qemu disk use writeback don't take effect in centos 7.2 1511 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paul Schlacter Cc: qemu-devel@nongnu.org * Paul Schlacter (wlfightup@gmail.com) wrote: > qemu version: 2.9.0 > image: centos 7.2 1511 raw > cache mode: writeback > > > In centos7.2 time, the use of writeback and none, the result of dd disk is > the same io, no change > > But I replaced centos7.1 centos7.3 centos7.4 when writeback was > significantly faster than none > > Would like to ask what is going on, how to solve ? Hi Paul, Can you just clarify your setup please; do you mean that with the same qemu setup but a 7.2 guest rather than a 7.1/7.3 guest the behaviour changes? Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK