RE: Feedback and question re Java memory/GC settings for Jmeter load generator CPU issue

[Antony Bowesman]

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.

Cheers
Antony


> -Original Message-
> From: Kirk Pepperdine [mailto:kirk.pepperd...@gmail.com]
> Sent: Monday, 19 March 2018 4:39 PM
> To: JMeter Users List 
> 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
>  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
> >
> >
> >
> >
> >
> >
> >


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Jmeter load test against AWS and nginx

[John Melom]

Has anyone run into throttling issues running a load test against AWS and / or 
nginx?

When we run a Jmeter load test against our AWS / nginx configuration, varying 
percentages of our http requests are subjected to a 1 second sleep server side. 
 Right now, our best analysis indicates it to be a nginx "denial of service 
attack" detection issue.  We have tried various nginx tuning settings, but 
haven't been able to make the issue go away.

I'm not sure how to make IP spoofing work from a linux load generation machine.

I'm curious if others have run into this issue and found ways to get around it.

Thanks,

John Melom




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