From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm@xmission.com (Eric W. Biederman) Subject: Re: Early SPECWeb99 results on 2.5.33 with TSO on e1000 Date: 11 Sep 2002 09:31:53 -0600 Sender: netdev-bounce@oss.sgi.com Message-ID: References: <477096648.1031728254@[10.10.2.3]> <20020911.081521.103561835.davem@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: mbligh@aracnet.com, hadi@cyberus.ca, tcw@tempest.prismnet.com, linux-kernel@vger.kernel.org, netdev@oss.sgi.com, niv@us.ibm.com Return-path: To: "David S. Miller" In-Reply-To: <20020911.081521.103561835.davem@redhat.com> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org "David S. Miller" writes: > From: ebiederm@xmission.com (Eric W. Biederman) > Date: 11 Sep 2002 09:06:36 -0600 > > "Martin J. Bligh" writes: > > > We can push about 420MB/s of IO out of this thing (out of that > > theoretical 800Mb/s). > > Sounds about average for a P3. I have pushed the full 800MiB/s out of > a P3 processor to memory but it was a very optimized loop. > > You pushed that over the PCI bus of your P3? Just to RAM > doesn't count, lots of cpu's can do that. > > That's what makes his number interesting. I agree. Getting 420MB/s to the pci bus is nice, especially with a P3. The 800MB/s to memory was just the test I happened to conduct about 2 years ago when I was still messing with slow P3 systems. It was a proof of concept test to see if we could plug in an I/O card into a memory slot. On a current P4 system with the E7500 chipset this kind of thing is easy. I have gotten roughly 450MB/s to a single myrinet card. And there is enough theoretical bandwidth to do 4 times that. I haven't had a chance to get it working in practice. When I attempted to run to gige cards simultaneously I had some weird problem (probably interrupt related) where adding additional pci cards did not deliver any extra performance. On a P3 to get writes from the cpu to hit 800MB/s you use the special cpu instructions that bypass the cache. My point was that I have tested the P3 bus in question and I achieved a real world 800MB/s over it. So I expect that on the system in question unless another bottleneck is hit, it should be possible to achieve a real world 800MB/s of I/O. There are enough pci busses to support that kind of traffic. Unless the memory controller is carefully placed on the system though doing 400+MB/s could easily eat up most of the available memory bandwidth and reduce the system to doing some very slow cache line fills. Eric