From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:58574) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S9vfW-0006qV-Qz for qemu-devel@nongnu.org; Tue, 20 Mar 2012 05:48:02 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S9vfE-0003fc-UA for qemu-devel@nongnu.org; Tue, 20 Mar 2012 05:47:54 -0400 Received: from mail-pz0-f45.google.com ([209.85.210.45]:40216) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S9vfE-0003cZ-LX for qemu-devel@nongnu.org; Tue, 20 Mar 2012 05:47:36 -0400 Received: by dadp14 with SMTP id p14so12572333dad.4 for ; Tue, 20 Mar 2012 02:47:34 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <4F685230.9040209@redhat.com> Date: Tue, 20 Mar 2012 10:47:28 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1331603611-9103-1-git-send-email-zwu.kernel@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] block: add the support to drain throttled requests List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Zhi Yong Wu Cc: Kevin Wolf , Zhi Yong Wu , qemu-devel@nongnu.org, stefanha@linux.vnet.ibm.com Il 20/03/2012 10:40, Zhi Yong Wu ha scritto: > HI, Kevin, > > We hope that I/O throttling can be shipped without known issue in QEMU > 1.1, so if you are available, can you give this patch some love? I'm sorry to say this, but I think I/O throttling is impossible to save. As it is implemented now, it just cannot work in the presence of synchronous I/O, except at the cost of busy waiting with the global mutex taken. See the message from Stefan yesterday. Unfortunately I don't have any solution for this, except perhaps disabling throttling around synchronous I/O. Paolo