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From Nick Kew <n...@webthing.com>
Subject Re: [users@httpd] Page generation time
Date Thu, 15 Jan 2004 01:54:43 GMT
On Wed, 14 Jan 2004, Franck Lefebure wrote:

> Hi,
>
> Do you know a way (apache module, configuration ...) to measure the
  time between
> the request and the response of apache ?

I wrote a module that does that, among other things, for Apache 1.3,
giving timings in milliseconds.  A similar module for 2.0 would be
easier, with some caveats.

Because this was work done for a Client, I'm not at liberty to share
the source.  But I could perhaps condense the relevant functionality
into a module for you.

Now, the caveats: do you really know what you're measuring?

Apache 2 has a pipelined architecture.  That means it can start sending
the response before it has received the entire request.  Diagrammatically
we might represent it as:

Input:         |--------------------------------|
Processing:          |-------------------------------|
Output:                    |-------------------------------|

In fact, if we set aside reading the request headers, and buffering the
output, all I/O is managed from the handler.  And in many cases, it
dominates the request time, taking much longer than the processing.

That's not always an issue: many handlers break pipelining.
But you need to bear it in mind.

-- 
Nick Kew


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