netdev - Re: [PATCH net-next] packet: respect devices with LLTX flag in direct xmit

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Date:	Fri, 28 Mar 2014 16:50:58 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	dborkman@...hat.com
Cc:	netdev@...r.kernel.org, brouer@...hat.com
Subject: Re: [PATCH net-next] packet: respect devices with LLTX flag in
 direct xmit

From: Daniel Borkmann <dborkman@...hat.com>
Date: Thu, 27 Mar 2014 16:38:30 +0100

> Quite often it can be useful to test with dummy or similar
> devices as a blackhole sink for skbs. Such devices are only
> equipped with a single txq, but marked as NETIF_F_LLTX as
> they do not require locking their internal queues on xmit
> (or implement locking themselves). Therefore, rather use
> HARD_TX_{UN,}LOCK API, so that NETIF_F_LLTX will be respected.
> 
> trafgen mmap/TX_RING example against dummy device with config
> foo: { fill(0xff, 64) } results in the following performance
> improvements for such scenarios on an ordinary Core i7/2.80GHz:
 ...
> Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
> Cc: Jesper Dangaard Brouer <brouer@...hat.com>

Applied, nice work.

The only remaining issue is that Eric seems to suggest that a tx
dropped counter bump should be added.  Please submit that as a
follow-on if my reading of his feedback is accurate.
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