-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Nikita,
On 4/16/2009 3:09 PM, dukehoops wrote: > In brief: > I am load-testing an app running on Tomcat 6 NIO and am observing a big > discrepancy between avg request latency as reported by JMeter (660ms) and > the profiler (19ms). I would like to understand where is the delta being > spent. > JMeter is simulating 40 users, each repeatedly hitting the server with the > same request (against port 8080), with 50ms think time. The response for > each request is in plain text, about 10-20k worth. The request hits > app-level cache 100% of the time, so JDBC connection aren't even being > checked out of the cxn pool and no DB work is being done. Assuming this is true, here is your raw data: Simultaneous “users” 40 Request Think Time (ms) 50 Response size (kB) 15 Network speed (ideal kbps) 1024 > Given the huge discrepancy, I would like to determine where is 642ms > (=661-19) being spent. Network latency should not be an issue. Not latency, but perhaps bandwidth: Request Freq (1/sec) 800 Response size (bits) 122880 Response bits per second 98304000 Network speed (bps) 1048576 You are trying to shove ~100 times more data through your network per second than it can handle. Also don't forget that actual ethernet bandwidth is more like 30% of the the "ideal", so you're talking about a network that can actually run at something around 315,000bps. Did you think that you wouldn't clog Teh Tubes with all that data? The Internet isn't like a big truck. > Is it > possible that Tomcat is spending time doing something in NIO poller - before > Tomcat's exec threads are engaged? Try backing-off your tests to the point where your network can keep up, and then see what your test report. - -chris -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkns7BQACgkQ9CaO5/Lv0PCVGACgqA/umJr4kgXBSmPlCHl6LChe 3ksAn004amc0l6oCUi+u6y9dvhgtxhMM =mTzH -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
