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From Antony Blakey <>
Subject Re: Statistics Module
Date Fri, 30 Jan 2009 05:32:08 GMT

On 30/01/2009, at 9:56 AM, Paul Davis wrote:

> The way that stats are calculated currently with the dependent
> variable being time could cause some issues in implementing more
> statistics. With my extremely limited knowledge of stats I think
> moving that to be dependent on the number of requests might be better.
> This is something that hopefully someone out there knows more about.
> (This is in terms of "avg for last 5 minutes" vs "avg for last 100
> requests", (the later of the two making stddev type stats
> calculateable on the fly in constant memory.)

The problem with using # of requests is that depending on your data,  
each request may take a long time. I have this problem at the moment:  
1008 documents in a 3.5G media database. During a compact, the status  
in _active_tasks updates every 1000 documents, so you can imagine how  
useful that is :/ I thought it had hung (and neither the beam.smp CPU  
time nor the IO requests were a good indicator). I spent some time  
chasing this down as a bug before realising the problems was in the  
status granularity!

Antony Blakey
CTO, Linkuistics Pty Ltd
Ph: 0438 840 787

The ultimate measure of a man is not where he stands in moments of  
comfort and convenience, but where he stands at times of challenge and  
   -- Martin Luther King

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