From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:47917) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1USpjx-0006Di-Of for qemu-devel@nongnu.org; Thu, 18 Apr 2013 10:23:26 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1USpjn-0005mr-S7 for qemu-devel@nongnu.org; Thu, 18 Apr 2013 10:23:09 -0400 Received: from ssl.dlhnet.de ([91.198.192.8]:36106 helo=ssl.dlh.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1USpjn-0005lw-J0 for qemu-devel@nongnu.org; Thu, 18 Apr 2013 10:22:59 -0400 Message-ID: <517001C1.8050005@dlhnet.de> Date: Thu, 18 Apr 2013 16:22:57 +0200 From: Peter Lieven MIME-Version: 1.0 References: <1365311880-11800-1-git-send-email-peter.crosthwaite@xilinx.com> <878v4kvt54.fsf@codemonkey.ws> In-Reply-To: <878v4kvt54.fsf@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] mainloop.c: Keep unlocking BQL during busy-wait spin-out List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: pbonzini@redhat.com, Peter Crosthwaite , qemu-devel@nongnu.org On 15.04.2013 15:08, Anthony Liguori wrote: > Peter Crosthwaite writes: > >> Modify Anthony's starvation detection logic to keep the BQL unlocked >> until the starvation condition goes away. Otherwise the counter has to >> count up to 1000 for each needed iteration until the busy-wait is >> lifted. >> >> Reset the counter back to zero once glib_pollfds_fill returns with a >> non-zero timout, (indicating a return to normality). The 1000 iteration >> wait now only happens once on the transition from normal operation to >> busy-wait starvation. >> >> Anthony's original patch fixed the serial paste bug, but this patch is >> also needed to restore performance. >> >> Signed-off-by: Peter Crosthwaite > I'm going through patches for 1.5 candidates. > > I believe the paste performance issue has been resolved now and this > patch is no longer needed. I can't find a definitive statement on the > list for that though. I am also hitting a problem that occured first after Anthonys original patch. In my testing environment I had 3 vServers that indepently of the load became heavily unresponsive after reporting "main-loop: WARNING: I/O thread spun for 1000 iterations". Even QMP is not responsing from time to time. But I am not using serial. From the load statistics it seems that the vServers is using one complete core busy waiting. I haven't seen this before this patch. Peter