From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aurelien Jarno Subject: Re: Network performance regression between kvm-29 and kvm-31 Date: Sun, 22 Jul 2007 15:29:32 +0200 Message-ID: <20070722132932.GF16993@hall.aurel32.net> References: <20070720222545.GB22656@hall.aurel32.net> <20070720225813.GA24368@hall.aurel32.net> <46A1A610.2050603@qumranet.com> <46A1BA2D.30800@aurel32.net> <46A331B6.7020306@qumranet.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Avi Kivity Return-path: Content-Disposition: inline In-Reply-To: <46A331B6.7020306-atKUWr5tajBWk0Htik3J/w@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org On Sun, Jul 22, 2007 at 01:30:14PM +0300, Avi Kivity wrote: > Aurelien Jarno wrote: > >>> > >>> I finally didn't resist to run git bisect before going to bed... > >>> > >>> The patch that causes the regression is: > >>> > >>> commit 7d2e674835492040c9baddf0989a95abea9a8d0f > >>> Author: Avi Kivity > >>> Date: Sun Jul 15 15:08:23 2007 +0300 > >>> > >>> kvm: qemu: synchronous signal handling > >>> > >>> in order to ensure that signals are handled with the global lock held, we > >>> block them, and dequeue them with sigtimedwait(). we can then call the > >>> handlers directly. > >>> > >>> this ensures that the device model and internal qemu data structures are not > >>> corrupted by cpu 0 thread handling a signal while cpu 1 is servicing a pio > >>> or mmio request. > >>> > >>> > >>> > >> Is this with -net user or -net tap? > >> > >> > > > > With -net tap. > > > > > > I pushed a commit which fixes a latency issue with that commit. However > with my test (ping -f against the host) I only get a x2 performance > increase. Can you test kvm-userspace.git? And can you detail your > benchmark? Yes, that fixes the problem. However it seems it has broken SMP support, I am not able to boot a linux guest with 2 CPU with this patch. About my benchmark, I am just copying a big file using scp between the guest and the host, and I saw a drop from 7,5 MiB/s to 280 kiB/s. Aurelien -- .''`. Aurelien Jarno | GPG: 1024D/F1BCDB73 : :' : Debian developer | Electrical Engineer `. `' aurel32-8fiUuRrzOP0dnm+yROfE0A@public.gmane.org | aurelien-rXXEIb44qovR7s880joybQ@public.gmane.org `- people.debian.org/~aurel32 | www.aurel32.net ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/