From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bin Ren Subject: Re: [PATCH] Network Checksum Removal Date: Mon, 23 May 2005 22:01:59 +0100 Message-ID: <8ae780250505231401729e40a3@mail.gmail.com> References: Reply-To: bin.ren@cl.cam.ac.uk Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ian Pratt Cc: xen-devel@lists.xensource.com, Andrew Theurer , Jon Mason List-Id: xen-devel@lists.xenproject.org Machines spec: External server: CPU: L1 I Cache: 64K (64 bytes/line), D cache 64K (64 bytes/line) CPU: L2 Cache: 1024K (64 bytes/line) CPU: AMD Athlon(tm) 64 Processor 3200+ stepping 08 Memory: 1024M DDR400 CAS 3 NIC: 1Gb/s Intel Pro/1000 MT Desktop Xen machine: CPU: L1 I Cache: 64K (64 bytes/line), D cache 64K (64 bytes/line) CPU: L2 Cache: 256K (64 bytes/line) CPU: AMD Sempron(tm) 2200+ stepping 01 Memory: 1024M DDR400 CAS 3 NIC: 1Gb/s Intel Pro/1000 MT Desktop The highest number I'm seeing here is 760Mbps running native linux on the Xen machine. dom0->external server gets 650Mbps. dom1->external server is definitely low using the default BVT. I've recently implemented a Xen scheduler based on Earliest Eligible Virtual Deadline First, which gives 610Mbps for dom1->external, ~50% improvement over BVT. I'm still figuring out why. On 5/23/05, Ian Pratt wrote: > > Overall though these are the kind of results I would expect. > > Linux usually does csumming at the same time as it has to do > > a copy anyway, and it ends up being limited by > > memory/L2-cache bandwidth, not the extra computation. But the > > offload extensions haven't cost much to implement and there > > are probably cases where it helps a little. > > > > Maybe I'm being pessimistic though: Can you reproduce the > > rather more impressive speedups that you previously saw, Jon? >=20 > We should be getting some benefit on the receive path, where the > checksum is normally forced to happen independent of a copy. Having this > offloaded to hardware should produce some measureable gain. >=20 > Bin: The numbers you're seeing are terrible anyway. You should be seeing > 890Mb/s for external traffic. What kind of machine is this on? >=20 > Ian >