From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Stevens Subject: Re: [RFC][ PATCH 0/3] vhost-net: Add mergeable RX buffer support to vhost-net Date: Wed, 3 Mar 2010 00:54:25 -0800 Message-ID: References: <20100303075432.GA14034@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Cc: kvm@vger.kernel.org, netdev@vger.kernel.org, rusty@rustcorp.com.au, virtualization@lists.osdl.org To: "Michael S. Tsirkin" Return-path: In-Reply-To: <20100303075432.GA14034@redhat.com> Sender: kvm-owner@vger.kernel.org List-Id: netdev.vger.kernel.org "Michael S. Tsirkin" wrote on 03/02/2010 11:54:32 PM: > On Tue, Mar 02, 2010 at 04:20:03PM -0800, David Stevens wrote: > > These patches add support for mergeable receive buffers to > > vhost-net, allowing it to use multiple virtio buffer heads for a single > > receive packet. > > +-DLS > > > > > > Signed-off-by: David L Stevens > > Do you have performance numbers (both with and without mergeable buffers > in guest)? Michael, Nothing formal. I did some TCP single-stream throughput tests and was seeing 20-25% improvement on a laptop (ie, low-end hardware). That actually surprised me; I'd think it'd be about the same, except maybe in a test that has mixed packet sizes. Comparisons with the net-next kernel these patches are for showed only ~10% improvement. But I also see a lot of variability both among different configurations and with the same configuration on different runs. So, I don't feel like those numbers are very solid, and I haven't yet done any tests on bigger hardware. 2 notes: I have a modified version of qemu to get the VHOST_FEATURES flags, including the mergeable RX bufs flag, passed to the guest; I'll be working with your current qemu git trees next, if any changes are needed to support it there. Second, I've found a missing initialization in the patches I sent on the list, so I'll send an updated patch 2 with the fix, and qemu patches when they are ready (plus any code-review comments incorporated). +-DLS