From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58901) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XUyJf-0001xW-DH for qemu-devel@nongnu.org; Fri, 19 Sep 2014 09:33:45 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XUyJX-0006Aw-5w for qemu-devel@nongnu.org; Fri, 19 Sep 2014 09:33:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35317) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XUyJW-000699-Ue for qemu-devel@nongnu.org; Fri, 19 Sep 2014 09:33:31 -0400 Message-ID: <541C3095.4040405@redhat.com> Date: Fri, 19 Sep 2014 15:33:09 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1409935888-18552-1-git-send-email-pl@kamp.de> <1409935888-18552-5-git-send-email-pl@kamp.de> <541AE887.9050607@redhat.com> In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 4/4] block: avoid creating oversized writes in multiwrite_merge List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: kwolf@redhat.com, ronniesahlberg@gmail.com, qemu-devel@nongnu.org, stefanha@redhat.com, mreitz@redhat.com Il 19/09/2014 00:56, Peter Lieven ha scritto: >> > So I think if we treat it just as a hint for multiwrite, we can avoid >> > writing code to split oversized requests. They always worked so far, we >> > can certainly wait until we have a real bug fix. > I would not treat this as a hint. I would use it in cases where we definitely > know an absolute hard limit for I/O request size. Otherwise the value for > bs->bl.max_transfer_length should be 0. > > If there comes in an oversized request we fail it as early as possible That's the part that I'd rather not touch, at least not without doing request splitting. Paolo and regarding > the multi write code we avoid that it accidentally generates an oversized request.