netdev - RE: [PATCH net-next 1/2] bnx2x: add support for ndo_ll

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Date:	Tue, 18 Jun 2013 12:11:46 +0000
From:	"Dmitry Kravkov" <dmitry@...adcom.com>
To:	"Eric Dumazet" <eric.dumazet@...il.com>
cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Eilon Greenstein" <eilong@...adcom.com>
Subject: RE: [PATCH net-next 1/2] bnx2x: add support for ndo_ll_poll

> -----Original Message-----
> From: Eric Dumazet [mailto:eric.dumazet@...il.com]
> Sent: Tuesday, June 18, 2013 2:16 PM
> To: Dmitry Kravkov
> Cc: davem@...emloft.net; netdev@...r.kernel.org; Eilon Greenstein
> Subject: RE: [PATCH net-next 1/2] bnx2x: add support for ndo_ll_poll
> 
> On Tue, 2013-06-18 at 10:45 +0000, Dmitry Kravkov wrote:
> 
> > > Ideally, we could keep a counter of enabled LLS sockets, to
> > > automatically switch off/on GRO, but in net/core, not in every driver.
> >
> > Since we have GRO in FW it will be hard to disable/enable it on the fly, probably better  to return LL_FLUSH_FAILED when GRO is
> enabled?
> 
> Yes, assuming GRO in FW means latencies ?
> 
> (If we receive a frame, FW has to wait a bit for the following frames to
> eventually aggregate them)
That's true !

But problem is that in disabling the feature on the fly will be very SlowPath operation, which can't be done from poll callback...

> 
> I thought FW did LRO part on bnx2x, and GRO was the software thing (in
> networking core, not in the bnx2x drivre)

LRO has priority over GRO, when LRO is disabled bnx2x FW provides fully GRO-complaint  aggregations,
which are ready for forwarding without host cpu intervention... 

> 
> 
>