From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:51582) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TYJaH-0003wm-Gk for qemu-devel@nongnu.org; Tue, 13 Nov 2012 11:43:36 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TYJaE-00062d-EX for qemu-devel@nongnu.org; Tue, 13 Nov 2012 11:43:33 -0500 Received: from mx1.redhat.com ([209.132.183.28]:12201) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TYJaE-00062X-69 for qemu-devel@nongnu.org; Tue, 13 Nov 2012 11:43:30 -0500 Date: Tue, 13 Nov 2012 18:46:04 +0200 From: "Michael S. Tsirkin" Message-ID: <20121113164603.GA788@redhat.com> References: <24E144B8C0207547AD09C467A8259F75577EDCC2@lisa.maurer-it.com> <24E144B8C0207547AD09C467A8259F75577EE707@lisa.maurer-it.com> <6c17c45c1439f217b36df2c78f0a04e6.squirrel@ssl.dlhnet.de> <50A233AF.70107@dlhnet.de> <20121113162256.GA554@redhat.com> <20121113163331.GA645@redhat.com> <9C6C6934-ABF0-4BC2-A412-3E8B3DB59F81@dlhnet.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9C6C6934-ABF0-4BC2-A412-3E8B3DB59F81@dlhnet.de> Subject: Re: [Qemu-devel] slow virtio network with vhost=on and multiple cores List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: Stefan Hajnoczi , Peter Lieven , Jan Kiszka , Dietmar Maurer , "qemu-devel@nongnu.org" On Tue, Nov 13, 2012 at 05:35:55PM +0100, Peter Lieven wrote: > > Am 13.11.2012 um 17:33 schrieb Michael S. Tsirkin: > > > On Tue, Nov 13, 2012 at 06:22:56PM +0200, Michael S. Tsirkin wrote: > >> On Tue, Nov 13, 2012 at 12:49:03PM +0100, Peter Lieven wrote: > >>> > >>> On 09.11.2012 19:03, Peter Lieven wrote: > >>>> Remark: > >>>> If i disable interrupts on CPU1-3 for virtio the performance is ok again. > >>>> > >>>> Now we need someone with deeper knowledge of the in-kernel irqchip and the > >>>> virtio/vhost driver development to say if this is a regression in qemu-kvm > >>>> or a problem with the old virtio drivers if they receive the interrupt on > >>>> different CPUs. > >>> anyone? > >> > >> Looks like the problem is not in the guest: I tried ubuntu guest > >> on a rhel host, I got 8GB/s with vhost and 4GB/s without > >> on a host to guest banchmark. > >> > > > > Tried with upstream qemu on rhel kernel and that's even a bit faster. > > So it's ubuntu kernel. vanilla 2.6.32 didn't have vhost at all > > so maybe their vhost backport is broken insome way. > > That might be. I think Dietmar was reporting that he had problems > with Debian. They likely use the same back port. > > Is it correct that with kernel_irqchip the IRQs are > delivered to all vCPUs? Without kernel_irqchip (in qemu-kvm 1.0.1 > for instance) they where delivered only to vCPU 0. This scenario > was working. > > Peter You need to look at how MSI tables are programmed to check if it's OK - guest can program MSI to do it like that. pciutils does not do this unfortunately so you'll have to write a bit of C code if you want to do this. -- MST