If raw performance (time from "request-came-in" to "about-to-start-sending") is what you want to measure, in my humble opinion you should measure that on the server itself, not the client, otherwise the network will allways interfere with your measurements - in our current projects we send an X-header holding the processing time: X-Time: 0.017s

Mmmh. So is a http response alsways a combination of header+response and I have no handle to get into the data-chunks (and their timing) received by LWP::UserAgent?

I am not able to get on the server side. So my only chance is to calculate: ((overall-response-time / transferred-bytes) / my-network-throughput-capacity) or something like that to get a hint of the time used to prepare the response on the server side?

There's a Perl module: WWW::Curl at http://curl.haxx.se/libcurl/perl/

You could also just record the time at intervals in LWP::Protocol::http::request().

I am not so familar with the LWP internals and never came to the "LWP::Protocol" branch... How would I poll LWP::Protocol::http::request()? By getting the private $sel_timeout var? A code hint would be great!

I don't want to switch over to curl...

OK, do a:

   locate Protocol/http.pm
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or similar to find where your LWP::Protocol::http module lives. Mine is in /usr/share/perl5/LWP/Protocol/http.pm. Search for the request() subroutine. Add these lines up at the top of it:

   use Time::HiRes qw(time);
   my @times;
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Add a line containing "push @times, time();" before the following three lines:

   if ($has_content) { block, 
   ...
   $response = $self->collect($arg, $response, sub {
   ...
   unless ($drop_connection) {
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and then add this at the bottom:

   warn "wrote-request    read-headers     read-content\n@times\n";
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If this is anything but a quick hack, it might be better to subclass or otherwise hook into LWP::Protocol::http to make it more maintainable. Another approach would be to just do a HEAD and then a GET, with the difference in times being the content-transfer time.