netdev - Re: [PATCH net-next 2/2] bnx2x: add RSS capability for GRE traffic

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Date:	Sat, 17 Aug 2013 21:52:12 +0300
From:	Dmitry Kravkov <dkravkov@...il.com>
To:	Jerry Chu <hkchu@...gle.com>
Cc:	Dmitry Kravkov <dmitry@...adcom.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Eilon Greenstein <eilong@...adcom.com>,
	Tom Herbert <therbert@...gle.com>,
	Maciej Żenczykowski <maze@...gle.com>
Subject: Re: [PATCH net-next 2/2] bnx2x: add RSS capability for GRE traffic

On Sat, Aug 17, 2013 at 8:53 PM, Jerry Chu <hkchu@...gle.com> wrote:
> Dmitry,
>
> On Mon, Mar 18, 2013 at 11:30 PM, Dmitry Kravkov <dmitry@...adcom.com> wrote:
>>> -----Original Message-----
>>> From: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org] On Behalf Of Eric Dumazet
>>> Sent: Tuesday, March 19, 2013 2:08 AM
>>> To: Dmitry Kravkov
>>> Cc: davem@...emloft.net; netdev@...r.kernel.org; Eilon Greenstein; Tom Herbert; Maciej Żenczykowski
>>> Subject: Re: [PATCH net-next 2/2] bnx2x: add RSS capability for GRE traffic
>>>
>>> On Mon, 2013-03-18 at 18:51 +0200, Dmitry Kravkov wrote:
>>> > The patch drives FW to perform RSS for GRE traffic,
>>> > based on inner headers.
>>> >
>>> > Signed-off-by: Dmitry Kravkov <dmitry@...adcom.com>
>>> > Signed-off-by: Eilon Greenstein <eilong@...adcom.com>
>>> > ---
>>> >  drivers/net/ethernet/broadcom/bnx2x/bnx2x_cmn.h |    3 +++
>>> >  drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.c  |   23 ++++++++++++-----------
>>> >  drivers/net/ethernet/broadcom/bnx2x/bnx2x_sp.h  |    9 +++++++++
>>> >  3 files changed, 24 insertions(+), 11 deletions(-)
>>>
>>> This works very well.
>>>
>>> Problem is we skb_set_queue_mapping(skb, 0); in __skb_tunnel_rx()
>>>
>>> (this was a patch from Tom Herbert, commit
>>> 693019e90ca45d881109d32c0c6d29adf03f6447 (net: reset skb queue mapping
>>> when rx'ing over tunnel )
>>>
>>> Meaning we hit a single cpu for the GRO stuff in ip_gre.
>>>
>>> I have to think about it.
>>>
>>>
>>> Another question is :
>>>
>>> Can bnx2x check the tcp checksum if GRE encapsulated ?
>>>
>> Current HW can't provide this. Probably, it's possible to separate CSUM from GRO/TPA then stack will have to handle CSUM validation for huge packets. Is it worth?
>
> Could you elaborate on what you meant above? (I'm looking for any form
> of h/w assist for
> csum validation for GRO/TPA pkts since csum computation can be expensive and  as
> you said below CHECKSUM_COMPLETE is out of the question.)
>

Current bnx2x HW is not able to perform CSUM validation for
encapsulated packets, so in any case host needs to do that.
Today GRO/TPA feature depends on CSUM, but theoretically (i did not
investigate it) and probably HW can provide aggregated packets w/o
csum validation - this will save headers processing for host.


> Thanks,
>
> Jerry
>
>>
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