netdev - Re: [PATCH net-2.6] ixgbe: fix automatic LRO/RSC settings for low latency

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Message-ID: <AANLkTiktWb0gbWOVyQ8pV_JQOnGXPU7dBN0AIwNODXnU@mail.gmail.com>
Date:	Thu, 10 Jun 2010 13:17:11 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Andy Gospodarek <andy@...yhouse.net>
Cc:	netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Stanislaw Gruszka <sgruszka@...hat.com>, stable@...nel.org
Subject: Re: [PATCH net-2.6] ixgbe: fix automatic LRO/RSC settings for low 
	latency

On Thu, Jun 10, 2010 at 11:12, Andy Gospodarek <andy@...yhouse.net> wrote:
>
> This patch added to 2.6.34:
>
>        commit f8d1dcaf88bddc7f282722ec1fdddbcb06a72f18
>        Author: Jesse Brandeburg <jesse.brandeburg@...el.com>
>        Date:   Tue Apr 27 01:37:20 2010 +0000
>
>            ixgbe: enable extremely low latency
>
> introduced a feature where LRO (called RSC on the hardware) was disabled
> automatically when setting rx-usecs to 0 via ethtool.  Some might not
> like the fact that LRO was disabled automatically, but I'm fine with
> that.  What I don't like is that LRO/RSC is automatically enabled when
> rx-usecs is set >0 via ethtool.
>
> This would certainly be a problem if the device was used for forwarding
> and it was determined that the low latency wasn't needed after the
> device was already forwarding.  I played around with saving the state of
> LRO in the driver, but it just didn't seem worthwhile and would require
> a small change to dev_disable_lro() that I did not like.
>
> This patch simply leaves LRO disabled when setting rx-usecs >0 and
> requires that the user enable it again.  An extra informational message
> will also now appear in the log so users can understand why LRO isn't
> being enabled as they expect.
>
> Inconsistency of LRO setting first noticed by Stanislaw Gruszka.
>
> Signed-off-by: Andy Gospodarek <andy@...yhouse.net>
> CC: Stanislaw Gruszka <sgruszka@...hat.com>
> CC: stable@...nel.org
>
> ---
>  drivers/net/ixgbe/ixgbe_ethtool.c |   37 ++++++++-----------------------------
>  1 files changed, 8 insertions(+), 29 deletions(-)
>

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