From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=55560 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PkKDg-0001RL-Ko for qemu-devel@nongnu.org; Tue, 01 Feb 2011 12:40:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PkJw6-00078u-Du for qemu-devel@nongnu.org; Tue, 01 Feb 2011 12:22:39 -0500 Received: from e2.ny.us.ibm.com ([32.97.182.142]:52313) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PkJw6-00078n-BV for qemu-devel@nongnu.org; Tue, 01 Feb 2011 12:22:38 -0500 Received: from d01dlp01.pok.ibm.com (d01dlp01.pok.ibm.com [9.56.224.56]) by e2.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p11H4k47026844 for ; Tue, 1 Feb 2011 12:04:54 -0500 Received: from d01relay02.pok.ibm.com (d01relay02.pok.ibm.com [9.56.227.234]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id 8740072806B for ; Tue, 1 Feb 2011 12:22:36 -0500 (EST) Received: from d03av02.boulder.ibm.com (d03av02.boulder.ibm.com [9.17.195.168]) by d01relay02.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p11HMZsm447004 for ; Tue, 1 Feb 2011 12:22:36 -0500 Received: from d03av02.boulder.ibm.com (loopback [127.0.0.1]) by d03av02.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p11HMZ2C025163 for ; Tue, 1 Feb 2011 10:22:35 -0700 Message-ID: <4D484159.1040704@linux.vnet.ibm.com> Date: Tue, 01 Feb 2011 11:22:33 -0600 From: Michael Roth MIME-Version: 1.0 Subject: Re: [Qemu-devel] [PATCH 1/2] Add virtagent file system freeze/thaw References: <1296557928-30019-1-git-send-email-Jes.Sorensen@redhat.com> <1296557928-30019-2-git-send-email-Jes.Sorensen@redhat.com> <4D48182E.9030201@redhat.com> <4D481A73.7040006@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Jes Sorensen , qemu-devel@nongnu.org, agl@us.ibm.com On 02/01/2011 08:41 AM, Stefan Hajnoczi wrote: > On Tue, Feb 1, 2011 at 2:36 PM, Jes Sorensen wrote: >> On 02/01/11 15:34, Stefan Hajnoczi wrote: >>> On Tue, Feb 1, 2011 at 2:26 PM, Jes Sorensen wrote: >>>> I have to admit you lost me here, where do you get that 500ms time from? >>>> Is that the XMLRPC polling time or? I just used the example code from >>>> other agent calls. >>> >>> 500 ms is made up. I was thinking, "what would a reasonable polling >>> interval be?" and picked a sub-second number. >>> >>> Can you explain how the timeout in fsfreeze can happen? It's probably >>> because I don't know the virtagent details. >> >> Ah ok. >> >> From what I understand, the XMLRPC code is setup to timeout if the guest >> doesn't reply within a certain amount of time. In that case, the caller >> needs to poll to wait for the guest to complete the freeze. This really >> should only happen if you have a guest with a large number of very large >> file systems. I don't know how likely it is to happen in real life. > > Perhaps Michael can confirm that the freeze function continues to > execute after timeout but the client is able to send fsstatus() > requests? Ahh, yeah there's the confusion: we only execute one RPC at a time, so a polling function for a previous RPC won't work unless that RPC is being done concurrently, via fork()ing or something and communicating status via some method of IPC. I touched on possible approaches to dealing with this in the response I just sent to this patch. > > Stefan