netdev - Re: [PATCH net-next] dql: dql_queued() should write first to reduce bus transactions

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Date:	Fri, 26 Sep 2014 10:47:32 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Tom Herbert <therbert@...gle.com>,
	Linux Netdev List <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Toke Høiland-Jørgensen 
	<toke@...e.dk>, Florian Westphal <fw@...len.de>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Dave Taht <dave.taht@...il.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	brouer@...hat.com
Subject: Re: [PATCH net-next] dql: dql_queued() should write first to reduce
 bus transactions

On Thu, 25 Sep 2014 23:04:56 -0700
Eric Dumazet <eric.dumazet@...il.com> wrote:

[...]
> 
> It turned out the problem was caused by compiler trying to be
> smart, but involving a bad MESI transaction :
>
[...] 
> 
> I got an incredible 10 % gain [1] by making sure cpu do not attempt
> to get the cache line in Shared mode, but directly requests for
> ownership.
[...]
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> ---

I'm very impressed - thank you Eric for finding this!!!

Acked-by: Jesper Dangaard Brouer <brouer@...hat.com>

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer
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