[httperf] Statistics

Chris Wilson chris at aptivate.org
Tue Jan 30 03:15:48 PST 2007


Hi Martin,

On Mon, 29 Jan 2007, Martin Arlitt wrote:

> as you know the true median cannot be higher than the maximum.  however,
> httperf trades off a small amount of accuracy in order to reduce the
> memory required.  instead of keeping a list of all the connection times,
> it keeps a histogram; the median value that is reported is the middle of
> the bin that contains the median value.  for example, if the bin held
> all observed values from 4 to 5 ms, then the reported median would be
> 4.5ms, no matter where the observed values fell within the bin.

Thanks for the explanation. Would it make sense for httperf to report the 
median as "4 ms" or "4.5 +/- 1.0 ms" to avoid giving a false impression of 
the accuracy?

Cheers, Chris
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