netdev - Re: [PATCH] ixgbe: reduce PTP rx path overhead

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Date:	Thu, 25 Oct 2012 00:35:12 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Jiri Benc <jbenc@...hat.com>
Cc:	netdev@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	John Ronciak <john.ronciak@...el.com>,
	Andy Gospodarek <gospo@...hat.com>
Subject: Re: [PATCH] ixgbe: reduce PTP rx path overhead

On Wed, 2012-10-24 at 17:17 +0200, Jiri Benc wrote:
> Hw timestamping code caused performance regression in ixgbe driver
> when the
> timestamping is not enabled. The culprit is IXGBE_READ_REG call in the
> rx
> path which is executed for every received skb. This call is not needed
> when
> the timestamping is disabled or for non-ptp packets.
> 
> netperf results:
> 
> The ixge side of the connection was acting as a server, the netperf
> command
> line on the other side was:
> netperf -H 192.168.1.23 -T0,0 -t UDP_STREAM -l 20
> 
> The values below mean throughput as reported by netperf
> (local/remote), for
> 3 runs, with timestamping not enabled.
> 
> 3.7.0-rc1+ with CONFIG_IXGBE_PTP off:
> 5373.83 / 3329.32
> 5721.88 / 3033.89
> 5653.42 / 3112.38
> 
> 3.7.0-rc1+ with CONFIG_IXGBE_PTP on:
> 5233.64 / 1226.85
> 5448.67 / 1039.32
> 5421.36 / 1095.66
> 
> Patched 3.7.0-rc1+ with CONFIG_IXGBE_PTP on:
> 5594.72 / 2942.53
> 5428.95 / 3110.16
> 5343.56 / 3200.48
> 
> Reported-by: Jesper Brouer <jbrouer@...hat.com>
> Signed-off-by: Jiri Benc <jbenc@...hat.com>
> Signed-off-by: Andy Gospodarek <gospo@...hat.com>
> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe_ptp.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-) 

Thanks Jiri, I have added the patch to my queue.

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