netdev - Re: Performance regression on kernels 3.10 and newer

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Date:	Thu, 14 Aug 2014 13:46:02 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Rick Jones <rick.jones2@...com>
Cc:	Alexander Duyck <alexander.h.duyck@...el.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: Performance regression on kernels 3.10 and newer

On Thu, 2014-08-14 at 12:59 -0700, Rick Jones wrote:

> Presumably, the -T $i,$j option in Alex's netperf command lines will 
> have bound netperf and netserver to a specific CPU where they will have 
> remained.

Thats the problem.

Softirq are receiving packets from other cpus. (RX queue X is handling
packets and one cpu is generally draining RX queue X and feed stack with
packets)

With RFS, RX path of IP and TCP stack would been handled by cpu Y (where
user thread is bound)



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