On 14 September 2011 19:20, Nicholson, Brad (Toronto, ON, CA) <bnichol...@hp.com> wrote: >> -----Original Message----- >> From: sebb [mailto:seb...@gmail.com] >> Sent: Wednesday, September 14, 2011 1:29 PM >> To: JMeter Users List >> Subject: Re: Startup Cost on first operation >> >> On 14 September 2011 17:57, Nicholson, Brad (Toronto, ON, CA) >> <bnichol...@hp.com> wrote: >> >> -----Original Message----- >> >> From: sebb [mailto:seb...@gmail.com] >> >> Sent: Wednesday, September 14, 2011 11:27 AM >> >> To: JMeter Users List >> >> Subject: Re: Startup Cost on first operation >> >> >> >> On 14 September 2011 16:14, Nicholson, Brad (Toronto, ON, CA) >> >> <bnichol...@hp.com> wrote: >> >> > Hi, >> >> > >> >> > I am using jmeter 2.5 and I am triggering my test via Ant and >> using >> >> the Jenkins Performance Plugin to display the data. >> >> > >> >> > With each test I run, the first result has heavily inflated times >> >> (hundreds of milliseconds instead of a few). I'd like to avoid >> having >> >> such high numbers in the initial operation. Google seems to imply >> that >> >> this is paying the complication time of the jmeter script during >> this >> >> operation. >> >> >> >> Do you mean compilation time? >> > >> > Sorry, yes - I mean compilation time. >> > >> > >> >> If so, that is done before the sample is started; sample times >> include >> >> only the time needed to perform the sample. >> >> >> >> > I can absorb the cost of this operation by adding a dummy >> operation >> >> at the start of the test, but I am wondering if there is a >> >> simpler/cleaner way of doing this? >> >> >> >> That should not be necessary; there must be something else happening >> >> here. >> >> >> >> Try using a Java sampler. Does the first sample take longer than the >> >> next? >> > >> > No - they are fairly uniform >> > >> >> What happens if you add a dummy before that? >> > >> > Dummy request takes a higher startup time, no change the Java >> request. >> > >> > All my requests (including the dummy request) are HTTP Request's and >> are connecting via https. >> >> https is much more expensive in connection setup >> >> >> Are you sure that the Jenkins Performance plugin is measuring >> samples, >> >> and not JMeter startup time? >> > >> > I'm sure it's not. I've confirmed by checking the raw output files >> written by Jmeter. To completely eliminate other moving pieces, I've >> re-run the test repeatedly directly from Jmeter and I see the same >> behavior. >> >> The only thing I can think of that might be causing the problem is the >> connection setup. >> First time JMeter init for a connection will be slightly slower, but >> should barely be noticeable; it will be the external stuff that takes >> the most time. >> And that will apply to browsers as well. >> >> Does the additional time apply to other target hosts? > > Yes - I've run it against a number of different hosts and the first request > is always significantly higher. > > >> Which sampler are you using? > > HTTP Request
Yes, but which implementation? Java, HttpClient3.1, HttpClient4? >> Are you using Keep-Alive? > > Yes > >> If you switch it off, each sampler will have to create the connection >> anew, so I would expect all the samples to take longer. > > I tried with keep alive off and there is no statistically interesting > difference. First operation is always around 600ms, all subsequent run > between 8ms to 25ms. It's the same for both keep-alive enabled and disabled. > I've tested with a variety of URL's btw, and the result is always the same. Are some of these URLs public? If so, can you create a Bugzilla issue and attach the JMX test script? >> AFAIK, JMeter itself does not do any expensive first-time init for >> either https or http (obviously if it does that should be fixed to >> exclude that time). >> However connections do have a setup overhead, which will apply to any >> application, including browsers, and need to be included in the JMeter >> sample time. > > There seems to be something in Jmeter causing this. I tried testing some of > the same URL's with Apache Benchmark and I pay no startup cost on those tests. Or it could be Java. AFAIK AB is C code. > Brad. > > --------------------------------------------------------------------- > To unsubscribe, e-mail: jmeter-user-unsubscr...@jakarta.apache.org > For additional commands, e-mail: jmeter-user-h...@jakarta.apache.org > > --------------------------------------------------------------------- To unsubscribe, e-mail: jmeter-user-unsubscr...@jakarta.apache.org For additional commands, e-mail: jmeter-user-h...@jakarta.apache.org
