From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Xiaoliang \(David\) Wei" Subject: Re: packet re-ordering on SMP machines. Date: Mon, 26 Aug 2002 16:03:36 -0700 Sender: netdev-bounce@oss.sgi.com Message-ID: <009701c24d54$d27304a0$f1fa010a@weixl> References: <3D69AFE7.6020902@candelatech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Cc: Return-path: To: "Ben Greear" , "jamal" , "Cheng Jin" , "Cheng Hu" , "Steven Low" Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org Hi Ben and Jamal, Are you guys sure that getdayoftime per packet is a big overhead on Gbps connection? Do you compare the performance with getdayoftime per packet and without? I guess RFC 1323 specifies that each packet should have a timestamp (although not from getdayoftime). Also, what's your testbed's configuration, Ben? (I guess if we can use faster hardware to overcome this effect...) Thank you:) ps: I am working on some high speed TCP experiment and may want to make getdayoftime every packet... -David Xiaoliang (David) Wei Graduate Student in CS@Caltech http://www.cs.caltech.edu/~weixl ==================================================== ----- Original Message ----- From: "Ben Greear" To: "jamal" Cc: Sent: Sunday, August 25, 2002 9:34 PM Subject: Re: packet re-ordering on SMP machines. > > jamal wrote: > > > That doesnt sound impressive at all. I know it's about .8 of wire rate > > but you should be able to exceed that. > > Robert was generating in the range of 800Kpps with that NIC if i recall > > corectly > > I had only tested 1514 byte pkts, so I was getting around 880Mbps, > which is pretty good as far as I know. > > I see about 255 kpps when sending 64 byte pkts to myself. Still > dropping about 1 in 4000 packets at this speed. I think most of Robert's > tests didn't involve actually doing something with the received packet > though, and I am inspecting it for latency, sequence number, etc. > > I'm even doing a __get_timeofday() call to calculate the latency...need > to find a faster way to do that... > > If I only allocate/scan 1 per 100 packets (ie alloc one packet and send it 100 times), > then I get a more respectable 365kpps. Robert's patch should definately help! > > > Also if you have SMP, tie each onto a CPU. > > That's with the irq_afinity thing in proc, right? > > > Additionaly get the skb recycler patch from Robert, it should improve > > things even more. > > Do you happen to have a URL for this? > > Actually, the various network tweaks are relatively hard to find > (at least to find the most up-to-date coppies). It would be great if > there was a place where they were all concentrated. > > > > > > >>Also, I see the hard_start_xmit call failing 5876 times out of 2719493 > >>calls (for example). The code that calls the method looks like this: > >> > > > > > > I dont have access to that NIC. But a stoopid question: Have you tried > > increasing the transmit queue via ifconfig? 1000 packets is reasonable > > for gige. > > I upped it, but it didn't stop the errors. The NIC is still performing, > so it may not be a real problem... > > Thanks for the info, > Ben > > -- > Ben Greear > President of Candela Technologies Inc http://www.candelatech.com > ScryMUD: http://scry.wanfear.com http://scry.wanfear.com/~greear > > > > >