netdev - Re: [PATCH 0/2] Get rid of ndo_xmit

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Message-Id: <20140827.135119.1651012580949456343.davem@davemloft.net>
Date:	Wed, 27 Aug 2014 13:51:19 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	cwang@...pensource.com
Cc:	netdev@...r.kernel.org, therbert@...gle.com, jhs@...atatu.com,
	hannes@...essinduktion.org, edumazet@...gle.com,
	jeffrey.t.kirsher@...el.com, rusty@...tcorp.com.au,
	dborkman@...hat.com, brouer@...hat.com
Subject: Re: [PATCH 0/2] Get rid of ndo_xmit_flush

From: Cong Wang <cwang@...pensource.com>
Date: Wed, 27 Aug 2014 11:28:25 -0700

> But for me, it looks like you are trying to pend some more packets
> in a TX queue until the driver decides to flush them all in one shot.
> So if that is true, doesn't this mean the latency of first packet pending
> in this queue will increase and network traffic will be more bursty for
> the receiver??

We intend to turn this so that it doesn't introduce latency.

The situation where we have the largest opportunity to perform
this batching is when the device queue has been stopped and is
started back up.

Usually at this moment the TX queue is %75 full and we have room
now for a couple of packets.

Therefore, delaying the triggering of the TX for this new set of
packets will have no effect on latency because the device is still
busy transmitting the rest of the TX queue.
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