netdev - Re: [PATCH net-next 0/5] qed/qede: Tunnel hardware GRO support

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Date:	Thu, 23 Jun 2016 04:10:53 +0000
From:	Yuval Mintz <Yuval.Mintz@...gic.com>
To:	Alexander Duyck <alexander.duyck@...il.com>,
	Eric Dumazet <eric.dumazet@...il.com>
CC:	Rick Jones <rick.jones2@....com>,
	Manish Chopra <manish.chopra@...gic.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Ariel Elior <Ariel.Elior@...gic.com>,
	Tom Herbert <tom@...bertland.com>,
	Hannes Frederic Sowa <hannes@...hat.com>
Subject: Re: [PATCH net-next 0/5] qed/qede: Tunnel hardware GRO support

>> Claiming that hardware assist GRO is not possible is a plain mantra.

> I have no issue claiming hardware assist GRO is possible.  My problem
> is saying that the GRO feature flag can be used to enable it.  I would
> argue that any packet aggregation at the device or driver level is LRO
> regardless of how close it comes to GRO feature wise.  GRO should only
> be occurring in the receive path after calling the appropriate GRO
> function.  Otherwise it becomes really difficult to work around any
> possible issues that the hardware assisted GRO introduces without
> paying a huge penalty.  We need to keep these feature flags separate.
> I thought that was the whole reason why we have the distinction
> between LRO and GRO in the first place.

Then again, if you're basically saying every HW-assisted offload on
receive should be done under LRO flag, what would be the use case
where a GRO-assisted offload would help?

I.e., afaik LRO is superior to GRO in `brute force' -
it creates better packed packets and utilizes memory better
[with all the obvious cons such as inability for defragmentation].
So if you'd have the choice of having an adpater perform 'classic'
LRO aggregation or something that resembles a GRO packet,
what would be the gain from doing the latter?