netdev - Re: rps testing questions

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Date:	Mon, 17 Jan 2011 10:53:14 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	mi wake <wakemi.wake@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: rps testing questions

Le lundi 17 janvier 2011 à 17:43 +0800, mi wake a écrit :
> I do a rps(Receive Packet Steering) testing on centos 5.5 with  kernel 2.6.37.
> cpu: 8 core Intel.
> ethernet adapter: bnx2x
> 
> Problem statement:
> enable rps with:
> echo "ff" > /sys/class/net/eth2/queues/rx-0/rps_cpus.
> 

bnx2x with one queue only ?

> running 1 instances of netperf TCP_RR: netperf  -t TCP_RR -H 192.168.0.1 -c -C
> without rps: 9963.48(Trans Rate per sec)
> with rps:  9387.59(Trans Rate per sec)
> 
> I do ab and tbench testing also find there is less tps with enable
> rps.but,there is more cpu using when with enable rps.when with enable
> rps ，softirqs is blanced  on cpus.

Really ? that seems unlikely with your one flow test, unless you _also_
have hardware IRQS hitting all your cpus. (That would be very bad)

> 
> is there something wrong with my test？
> --

If you test with one flow, RPS brings nothing at all. Better handle the
packet directly from the cpu handling the hardware IRQ (and NAPI)

You better make sure hardware IRQ are on one cpu, instead of many cpus.



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