[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Confusion regarding TC (cbq), policing and bursts

> Questions:
> 1.  I've gleaned from the net, that 'maxburst' refers to the number of
> bytes allowed in one burst.  Setting this value to much more than 100 seems
> to result in high packet loss.  But only 100bytes per burst?  Seems awfully
> small.

I think maxburst is the number of avpkt-sized packets allowed to be sent in a 
burst after a period when the source has been idle (anyone please correct me 
if I'm wrong)

> 2.  I've modified as per good advice found here and elsewhere, the PSCHED
> (now set to CPU) and HZ (now 1024) values.  What then, do those values
> mean? Why is one value better than another?

With the timer interrupt happening 1024 times per second instead of 100, you 
have a granularity that's about ten times smaller. This means you have better 
control over non-work-conserving qdiscs, as is the case of TBF.

> 3.  What is the sampling rate, ie:  how often does tc look at the packet
> stream to determine if a drop/accept action should occur?

Once per packet at enqueuing, although with some qdiscs it is possible to 
drop an already enqueued packet when enqueuing another. (Once again, correct 
me if I'm wrong)

Rui Prior