netdev - Re: rps perfomance WAS(Re: rps: question

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Date:	Fri, 16 Apr 2010 09:21:05 -0400
From:	jamal <hadi@...erus.ca>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Changli Gao <xiaosuo@...il.com>, Rick Jones <rick.jones2@...com>,
	David Miller <davem@...emloft.net>, therbert@...gle.com,
	netdev@...r.kernel.org, robert@...julf.net, andi@...stfloor.org
Subject: Re: rps perfomance WAS(Re: rps: question

On Fri, 2010-04-16 at 07:18 +0200, Eric Dumazet wrote:

> 
> A kernel module might do this, this could be integrated in perf bench so
> that we can regression tests upcoming kernels.

Perf would be good - but even softnet_stat cleaner than the the nasty
hack i use (attached) would be a good start; the ping with and without
rps gives me a ballpark number.

IPI is important to me because having tried it before it and failed
miserably. I was thinking the improvement may be due to hardware used
but i am having a hard time to get people to tell me what hardware they
used! I am old school - I need data;-> The RFS patch commit seems to
have more info but still vague, example: 
"The benefits of RFS are dependent on cache hierarchy, application
load, and other factors"
Also, what does a "simple" or "complex" benchmark mean?;->
I think it is only fair to get this info, no?

Please dont consider what i say above as being anti-RPS.
5 microsec extra latency is not bad if it can be amortized.
Unfortunately, the best traffic i could generate was < 20Kpps of
ping which still manages to get 1 IPI/packet on Nehalem. I am going
to write up some app (lots of cycles available tommorow). I still think
it is valueable.

cheers,
jamal

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