Am 19. März 2018 22:53:19 MEZ schrieb Antony Bowesman <[email protected]>: >Mmm, I saw the images had gone too :( > >I have set up to do a gc log next time I run the test and will dig into >it. I've been using the default Java8 GC, which is Parallel, so I am >going to use CMS to see if that makes a difference. I gather it is >supposed to favour shorter pauses, so I'll see what happens and post >back results.
As you have 12gb of heap, you could try to use g1, too. On the other hand side, this seems to be quite a lot of heap. What are you doing in your test plan? And as a nice plus, you could tell us about the used versions for jvm, jmeter and os. Regards, Felix > >Cheers >Antony > > >> -----Original Message----- >> From: Kirk Pepperdine [mailto:[email protected]] >> Sent: Monday, 19 March 2018 4:39 PM >> To: JMeter Users List <[email protected]> >> Subject: Re: Feedback and question re Java memory/GC settings for >Jmeter >> load generator CPU issue >> >> Hi, >> >> The images seem to have been filter out of my email at least. >> >> Can you collect and post a GC log. Most likely young gen is too small >but a gc >> log would confirm this. >> >> Kind regards, >> Kirk >> >> > On Mar 19, 2018, at 3:37 AM, Antony Bowesman >> <[email protected]> wrote: >> > >> > Hi, >> > >> > I just thought I’d send in some info about a problem I’ve been >looking at >> recently – with a question of best GC settings >> > >> > I have a number of JMeter load generators (LG) and I have been >seeing >> CPU spikes on the boxes during a test. I am monitoring CPU and memory >> from within a Java sampler, so have the following charts >> > >> > 1. First chart shows the request/sec rate (RHS axis) in blue >and the CPU >> max % in yellow (sampled every 5s). The blue vertical lines indicate >a drop in >> request rate (as recorded by the request finishing and therefore >being >> logged) an a corresponding spike to ‘catch up’. I note that the >spikes always >> correspond to a spike in CPU. >> > 2. The second shows the spikes appearing to correlate with >the increase >> in committed memory >> > 3. The third is after the JVM setting change. Note the >behaviour still >> occurs in CPU/request rate with a CPU spike in the green circle, but >not until >> the later stages. (NB: CPU scale is CPU% * 200 to fit on the graph) >> > >> > This behaviour is the same across all the LGs and happens >regardless of the >> way the target hosts are reached across the network, so I believe >it’s a >> JVM/host issue. >> > >> > The original memory settings were >> > >> > -Xms1G -Xmx12G -XX:NewSize=1024m -XX:MaxNewSize=4096m >> > >> > But I changed –Xms12G so that all memory is allocated initially and >that >> makes a huge change to the behaviour. >> > >> > However, I still see the CPU spike. Has anyone got some optimum GC >> settings they have used that can avoid this? >> > >> > Thanks >> > Antony >> > >> > >> > >> > >> > >> > >> > > > >--------------------------------------------------------------------- >To unsubscribe, e-mail: [email protected] >For additional commands, e-mail: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
