netdev - Re: [PATCH] net: Performance fix for process

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Message-ID: <1404156561.15139.72.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Mon, 30 Jun 2014 12:29:21 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <therbert@...gle.com>
Cc:	David Miller <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: Performance fix for process_backlog

On Mon, 2014-06-30 at 09:42 -0700, Tom Herbert wrote:

> Eliminating a couple of conditionals is a nice logic improvement, but
> is not material in the performance improvement. The improvement comes
> for the fact that we are staying in the the process_backlog loop and
> not clearing napi_state as long as there is still work to do. This can
> result in fewer IPIs which is shown in number of interrupts/sec.
> (1145382 vs. 1021674 in my test).
> 
> The cost of the change is one additional lock and check on qlen when
> the queue is empty, however in this case they should still be in the
> local cache so that's not overly expensive (far cheaper than more
> IPIs).

Great, thanks !


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