Thanks Tinca and Deepak for a vivid explanation. It's definitely worth to be a part of such active and talented forum where people are so enthusiastic to answer any queries.
Cheers!! Prasanna On Thu, Apr 15, 2010 at 4:02 AM, Deepak Shetty <[email protected]> wrote: > Hi > Other factors to consider is > a. What are you trying to test > For e.g. Suppose your application deadlocks sometimes and you need to > simulate this. In this case you might not want a ramp up time , you > actually > do want your application to be hit at the same time . On the other hand if > you are simulating actual user flows with think times then you dont want > 500 > threads to be created at the exact same moment since this probably isnt > normal for your application. Or say you are caching data on the first > request and the cache load is synchronized, then you might want to access > the page in multiple threads at the same time to check the synchronized > behavior so no ramp up. Or perhaps you want to see how many people can > download a large file at exactly the same time , you probably want to > check > with no rampup. > > b. If your test is a short test , then the results may be skewed negatively > without ramp-up (because both your client and server have to be able to > handle the initial burst of sockets/traffic). A ramp up also adds a certain > degree of randomness that your threads will be reasonably distributed > across > requests. > > Most tests where you want to measure the performance would want ramp up. > Most analysis sort of tests (like the deadlock/ cache tests) would not want > a ramp up. > > regards > deepak > > On Wed, Apr 14, 2010 at 10:09 AM, TincaTibo <[email protected]> wrote: > > > Hi, > > > > A ramp up period is necessary when your application can't handle all user > > connexions at the same time. > > Connecting everybody at the same time usually does a useless stress on > the > > server, that will generates bad response times, server hang, or worse, > > total > > failure. Because the servers have to create all the application context / > > thread / memory increase at once. > > > > To prevent that behaviour, ramp up is a good idea. Especially as in real > > life, users does not connect all at once. > > > > As for the timings, whith 5 users, and a ramp up of 5s, with 300s > duration: > > - after 5s, all your threads will be started > > - start rate at 1 / second approximately > > - each thread will last 300s > > - your test will end at 300 + 5 (time of last thread start) : that is to > > say > > : 305 s > > > > Play with it! > > > > Rgds, > > Tibo > > > > On Wed, Apr 14, 2010 at 17:10, prasanna bhat <[email protected] > > >wrote: > > > > > Hi, > > > > > > Description of Ramp Up period in the user manual : > > > This property tells JMeter how long to delay between starting each > user. > > > For > > > example, if you enter a Ramp-Up Period of 5 seconds, JMeter will finish > > > starting all of your users by the end of the 5 seconds. So, if we have > 5 > > > users and a 5 second Ramp-Up Period, then the delay between starting > > users > > > would be 1 second (5 users / 5 seconds = 1 user per second). If you set > > the > > > value to 0, JMeter will immediately start all users. > > > > > > Usecase description: > > > I have 5 users in the thread, a Ramp Up period set to 5 sec and the > > > duration set to 300 sec in the Scheduler configuration. So for the > first > > 5 > > > seconds each thread is invoked with a delay of 1 sec, but is the same > > > behavior(next thread is delayed for 1 sec) exhibited for the next 300 > > secs > > > of test duration? > > > > > > And also i was not clear as to how Ramp Up period is advantageous? and > > > when > > > to (and when not to) set this Ramp Up period? > > > > > > Thanks, > > > Prasanna > > > > > >
