netdev - Re: [PATCH net-next] net-rfs: fix false sharing accessing sd->input_queue

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Message-Id: <20160427.003131.1629120469234890217.davem@davemloft.net>
Date:	Wed, 27 Apr 2016 00:31:31 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net-rfs: fix false sharing accessing
 sd->input_queue_head

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 26 Apr 2016 15:30:07 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> sd->input_queue_head is incremented for each processed packet
> in process_backlog(), and read from other cpus performing
> Out Of Order avoidance in get_rps_cpu()
> 
> Moving this field in a separate cache line keeps it mostly
> hot for the cpu in process_backlog(), as other cpus will
> only read it.
> 
> In a stress test, process_backlog() was consuming 6.80 % of cpu cycles,
> and the patch reduced the cost to 0.65 %
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied, nice work Eric.