Subject: Re: multiple Tx queues
To: Greg Troxel <firstname.lastname@example.org>
From: Sam Leffler <email@example.com>
Date: 01/11/2004 11:07:30
On Sunday 11 January 2004 10:17 am, Greg Troxel wrote:
> The Atheros 5212-based cards support multiple xmit queues and
> implement a variety of queueing policies in h/w. This stuff is
> explicitly intended to supoprt QoS as set out, for example, the WME
> spec. Applications include VoIP and streaming video. To
> effectively use this stuff applications need to be able to tag
> packets and have the OS stay out of the way except to not smash the
> tag before it reaches the driver (where it can be used to select the
> appropriate queue).
> I haven't read the WME/802.11e specs yet.
> Why couldn't this be handled by an application setting the TOS (er,
> DSCP) with a setsockopt, and having the driver sort into queues based
> on the DSCP? If there is a qos mechanism for sending packets over
> wireless, then I would think it useful for it to work on packets
> originated on a wired host that are being forwarded by another host
> over wireless (e.g. connection sharing over Ethernet, etc. of a host
> with an 802.11 connection).
I thought I was saying basically this. Some ideas were floated for
configuring the mapping between traffic and priority and/or possible queueing
algorithms. I was just trying to point out that for some hardware this is
probably not useful. Having the OS doing anything is probably not very
helpful; just pass the packet down to the driver as quickly as possible so it
can stick it in the appropriate h/w queue.