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

Rick Jones rick.jones2 at hp.com
Tue Mar 15 14:31:59 PDT 2011

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 :)

rick jones

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