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

[Rick Jones]

On Tue, 2011-03-15 at 20:32 -0400, John W. Linville wrote:
> On Tue, Mar 15, 2011 at 02:31:59PM -0700, Rick Jones wrote:
> > On Tue, 2011-03-15 at 16:51 -0400, John W. Linville wrote:
> > > 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?
> > 
> > HP-UX's lanadmin (and I presume the nwmgr command in 11.31) command will
> > display the "classic" interface MIB stats, which includes the outbound
> > queue length.  What it does (or should do) for that statistic in the
> > face of a multi-queue device I've no idea :)
> 
> But that is capacity, right?  Not current occupancy?  I thought that
> was the outcome of an earlier thread?

No, HP-UX shows current occupancy on its interfaces.   I think it is
Cisco which shows capacity - at least that is my recollection of one of
the other discussions.

rick