From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46691) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ya3si-0006kA-9Z for qemu-devel@nongnu.org; Mon, 23 Mar 2015 11:03:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Ya3sc-0007k6-MR for qemu-devel@nongnu.org; Mon, 23 Mar 2015 11:03:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34547) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Ya3sc-0007ju-F2 for qemu-devel@nongnu.org; Mon, 23 Mar 2015 11:03:02 -0400 Message-ID: <55102AF5.4000006@redhat.com> Date: Mon, 23 Mar 2015 16:02:13 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1427088255-29885-1-git-send-email-famz@redhat.com> <20150323135612.GI9268@stefanha-thinkpad.redhat.com> <55101C22.6040108@redhat.com> <55102804.20808@redhat.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] block: Switch to host monotonic clock for IO throttling List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Kevin Wolf , Fam Zheng , Alberto Garcia , qemu-devel , Stefan Hajnoczi On 23/03/2015 16:00, Stefan Hajnoczi wrote: > On Mon, Mar 23, 2015 at 2:49 PM, Paolo Bonzini wrote: >> On 23/03/2015 15:28, Stefan Hajnoczi wrote: >>> I'd like to know what problems exactly this patch fixes. The test >>> case for throttling actually relies on the virtual clock so it can be >>> stepped deterministically. What other legitimate cases are there >>> where throttling is used outside a running qemu-system process? >> >> Alberto brought up block jobs. It is debatable whether block jobs >> should be stopped while the VM is. > > This patch is unrelated to block jobs. Block jobs use their own > ratelimiting mechanism and the realtime clock (not vm clock). Block jobs are also influenced by throttling though, if their underlying BDS is throttled. For example, streaming works by doing reads on a BDS that is also visible to the VM and might be throttled. Same for mirroring or active-layer commit. Paolo