netdev - Re: [RFC] New driver API to speed up small packets xmits

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Date:	Thu, 10 May 2007 14:50:19 -0700
From:	Gagan Arneja <gaagaan@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	dlstevens@...ibm.com, rick.jones2@...com, johnpol@....mipt.ru,
	krkumar2@...ibm.com, netdev@...r.kernel.org,
	netdev-owner@...r.kernel.org
Subject: Re: [RFC] New driver API to speed up small packets xmits

David Miller wrote:

> Right.
> 
> But I think it's critical to do two things:
> 
> 1) Do this when netif_wake_queue() is triggers and thus the
>    TX is locked already.
> 
> 2) Have some way for the driver to say how many free TX slots
>    there are in order to minimize if not eliminate requeueing
>    during this batching thing.

I don't think you can reliably do this. Jumbograms may end up taking 
more than one slot.

> 
> If you drop the TX lock, the number of free slots can change
> as another cpu gets in there queuing packets.

Can you ever have more than one thread inside the driver? Isn't 
xmit_lock held while we're in there?

--
Gagan

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