[Bloat] Random idea in reaction to all the discussion of TCP flavours - timestamps?

[John W. Linville]

On Tue, Mar 15, 2011 at 09:40:06PM +0200, Jonathan Morton wrote:
> 
> On 15 Mar, 2011, at 8:31 pm, John W. Linville wrote:
> 
> > If you don't throttle _both_
> > the _enqueue_ and the _dequeue_, then you could be keeping a nice,
> > near-empty tx queue on the host and still have a long, bloated queue
> > building at the device.
> 
> Don't devices at least let you query how full their queue is?

I suppose it depends on what you mean?  Presumably drivers know that,
or at least can figure it out.  The accuracy of that might depend on
the exact mechanism, how often the tx rings are replinished, etc.

However, I'm not aware of any API that would let something in the
stack (e.g. a qdisc) query the device driver for the current device
queue depth.  At least, I don't think Linux has one -- do other
kernels/stacks provide that?

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville at tuxdriver.com			might be all we have.  Be ready.