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: Sat, 21 Jul 2007 00:58:13 +0200 Message-ID: <20070720225813.GA24368@hall.aurel32.net> References: <20070720222545.GB22656@hall.aurel32.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Return-path: Content-Disposition: inline In-Reply-To: <20070720222545.GB22656-OqXK5JiLQY5aJl8KAwiEcA@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 Sat, Jul 21, 2007 at 12:25:45AM +0200, Aurelien Jarno wrote: > Hi, > > I have just noticed that there is a huge performance regression in > network transfers between kvm-29 and kvm-31. Using the RTL8139 emulated > card, I have seen the network speed has been divided by 27!!! I haven't > made precise speed measurements with other emulated card, but the > network speed has been reduced by the same order. > > Those tests have been done on a Core 2 CPU. > > After some tests I have seen that the problem lies in the user part. I > will do a git bisect tomorrow to find the patch that has caused the > problem, unless somebody already find it. 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. -- .''`. 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: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/