Re: rps perfomance WAS(Re: rps: question

[Eric Dumazet <eric.dumazet@gmail.com>]

Le mardi 20 avril 2010 à 08:02 -0400, jamal a écrit : 
> folks,
> 
> Thanks to everybody (Eric stands out) for your patience. 
> I ended mostly validating whats already been said. I have a lot of data
> and can describe in details how i tested etc but it would require
> patience in reading, so i will spare you;-> If you are interested let me
> know and i will be happy to share.
> 
> Summary is: 
> -rps good, gives higher throughput for apps
> -rps not so good, latency worse but gets better with higher input rate
> or increasing number of flows (which translates to higher pps)
> -rps works well with newer hardware that has better cache structures.
> [Gives great results on my test machine a Nehalem single processor, 4
> cores each with two SMT threads that has a shared L2 between threads and
> a shared L3 between cores]. 
> Your selection of what the demux cpu is and where the target cpus are is
> an influencing factor in the latency results. If you have a system with
> multiple sockets, you should get better numbers if you stay within the
> same socket relative to going across sockets.
> -rps does a better job at helping schedule apps on same cpu thus
> localizing the app. The throughput results with rps are very consistent
> and better whereas in non-rps case, variance is _high_.
> 
> My next step is to do some forwarding tests - probably next week. I am
> concerned here because i expect the cache misses to be higher than the
> app scenario (netdev structure and attributes could be touched by many
> cpus)
> 

Hi Jamal

I think your tests are very interesting, maybe could you publish them
somehow ? (I forgot to thank you about the previous report and nice
graph)

perf reports would be good too to help to spot hot points.