First: measurement:
Apache access log can use "%D" in the LogFormat, which for Apache httpd
2.0 and 2.2 gives microseconds response time. Obviously the real
resolution depends on the operating system. The 15msec you mentioned is
way to long for a OS timer resultion.
mod_jk provides an apache "note" named JK_REQUEST_DURATION, which you
can include as "%{JK_REQUEST_DURATION}n" again in the access log of
Apache httpd. This measures Tomcat overall response time from the point
of view of mod_jk (microseconds formatted as seconds.micro).
Finally Tomcat itself can log milliseconds via "%D" in his access log.
But: when you talk about 4ms transaction time, it's more about latency,
which is only one aspect of performance. Usually latency is only
important if it gets to big, but decreasing latency below the OK level
is not very important. If latency is below an OK level, troughput is
more important wrt. performance.
throuput * response time = parallelism
In general if you want to measure throughput in a real life throughput
driven system, you need to increase the client parallelism to find out
how much throughput you can achieve. Response time (latency) will go up
too, but in some parallelism range, throughput will increase more.
If you add a component like httpd/mod_jk to the system, it will increase
latency. If your transactions are very fast, the added latency might be
relatively huge. In terms of throughput this will usually not produce a
penalty, and in some cases, if you can effectively use the features of
the added component, throughput might go up.
Regards,
Rainer
Tony Anecito wrote:
Hi All,
As I mentioned in my previous email I was able to get
my system performance using Apache-Tomcat-Jre1.6 such
that I was getting 4msec transaction response times.
My problem is I can not tell how much of that response
time is spent in tomcat versus Apache. I am using
windows 2000 where the configuration is Apache -
(Tomcat embedded in JBoss 4.2.1) using Mod_jk. The
problem I can measure the transaction in the servlet
which is in the sub-microsecond range but at apache
access logs or in the mod_jk logs I am seeing either 0
or 15msec. I suspect that is due to the timers used by
Apache.
I would like to know how long Tomcat is taking for the
request. I am using web services inside of Tomcat so
the request goes through that layer.
Also, can anyone tell me the performance differences
they have see when Tomcat is running on Linux versus
Windows? I have heard anything between 1 to 30%
improvment.
Also, any hints on how to improve Tomcat performance
appreciated.
Regards,
Tony
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