Response time without client network delay

[Anantha Padmanabha <anantha.padmanabha@xxxxxxxxxxxxxx>]

Hi,

I'm using Apache 2.2.8 and use %D to capture response times.

We did performance testing on newly purchased servers and made the same machines go live. 
Our latencies in production were greater than that of our perf run, even though requests were much lower.
Then we figured out that client delays also factor in the response time and our production clients are calling from slower network.
[This was confirmed again when we ran perf runs on production from clients with different outgoing bandwidth]

So, we need a way to measure response time excluding client, to know apaches performance. I've read http://httpd.apache.org/docs/2.0/mod/mod_log_config.html.
 Does %s do exactly this? [%s does not log in millisecs unfortunately]

Is there a way to get just the apache processing time [without client's network] in milli/micro seconds?

Thanks
Anantha