netdev - Re: [RFC v2 3/3] iwlwifi: mvm: transfer the truesize to the last TSO segment

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Date:	Thu, 20 Aug 2015 12:55:31 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Grumbach, Emmanuel" <emmanuel.grumbach@...el.com>
Cc:	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"ido@...ery.com" <ido@...ery.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Sharon, Sara" <sara.sharon@...el.com>
Subject: Re: [RFC v2 3/3] iwlwifi: mvm: transfer the truesize to the last
 TSO segment

On Thu, 2015-08-20 at 19:34 +0000, Grumbach, Emmanuel wrote:

> 
> Err... no :( It won't work for me because the MSS impacts the number of
> segments which in turns impact the number of time the headers have to be
> copied which impacts... the A-MSDU maximal size which must be bigger
> than gso_max_size. So basically, a connection parameter (MSS) impacts a
> device parameter (gso_max_size). Now, of course, I could give up on
> small MSS connections and skb_gso_segment() skbs whose MSS is smaller
> than the default. This means that I give up on LSO in certain cases...
> 

We also have dev->gso_max_segs for this kind of problems.

Really, you should take closer look.

And _if_ some LSO packets must be segmented using skb_gso_segment()
in some rare cases, who cares ?

> I will get back to the drawing board and check what I can do to use /
> enhance the core infra... But it will be hard to lose functionality /
> efficiency just to use the core infra...

Please take your time. Pushing hard some local hacks is not sustainable.


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