[Click] AverageCounter bug

[Egi, Norbert]

Hi,
 
Have you recognized after you patched the averagecounter.cc that if you divide the number of arrived packets (/proc/click/ctr/count) by the rate (/proc/click/ctr/rate) then you get an integer number all the times, which I think it's not very realistic?  I think this is because of the line 'd /= CLICK_HZ;' you added to the code. As a consequence, this makes the counter quite inaccurate, especially at high pps rates.
 
I made a tiny modification to your patch (attached to this email), check it out, this isn't the perfect solution either, but more accurate. Actually its accuracy is +-(CLICK_HZ) which was at my machine 250, but I'm not sure from where it comes from and whether it is the same all the time.
 
Norbert

________________________________

From: click-bounces at pdos.csail.mit.edu on behalf of rchertov at purdue.edu
Sent: Thu 1/4/2007 22:34
To: click at pdos.csail.mit.edu
Subject: Re: [Click] AverageCounter bug



I forgot the division by zero check in the previous patch.  The attached patch
handles that case.

Roman

Quoting rchertov at purdue.edu:

> Hello,
>    I noticed a bug with the AverageCounter when it would not report correct
> rates.  This usually would happen at GigE speeds when at least 10 million
> packets are sent.  The reported result would be much smaller than the actual
> true rate.  I have attached a fix that fixes the problem.  Previously I
> would
> get numbers that would sort of wrap around.
>
> E.X
> more /click/ctr/rate
> 600000
> more /click/ctr/rate
> 50000
> more /click/ctr/rate
> 23000
> more /click/ctr/rate
> 500000
>
> Now, it turns out that I can send 1.5 million pps from one card to another on
> my
> machine.  I have also tested this fix for a variety of rates from udpgen and
> the
> reported rates from the counter are close to the desired rate.  Also at very
> high rates UDPGen can be off by as much as 50Kpps from the desired rate.
>
> Roman Chertov




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