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Memory And Threads

Adil qureshi
Hi Guys,

Greeting for the day.


I am getting better performance with 25 threads than 30 threads and the performance of grinder keeps on decreasing if I increase the number of threads.

The system from which I am running grinder is a Solaris server and has high CPU capability as well as RAM.

If I start more than one process and divide the threads among them the no of calls that grinder can make even decreases.

I am trying to achieve a particular load which has become impossible as of now  with threads so limited.


Any suggestions on this will be highly appreciated.

Thanks In Advance,

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Re: Memory And Threads

Gary Mulder-3
On 31 August 2014 21:14, Adil qureshi <[hidden email]> wrote:

Any suggestions on this will be highly appreciated.

Try this: 


Gary

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Re: Memory And Threads

Adil qureshi

Hi,
Thanks for replying.
I have done this no improvement.

On 31 Aug 2014 21:27, "Gary Mulder" <[hidden email]> wrote:
On 31 August 2014 21:14, Adil qureshi <[hidden email]> wrote:

Any suggestions on this will be highly appreciated.

Try this: 


Gary

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Re: Memory And Threads

Gary Mulder-3
On 31 August 2014 21:37, Adil qureshi <[hidden email]> wrote:

Hi,
Thanks for replying.
I have done this no improvement.

Turning on the logging without examining what the log is indicating probably will provide no improvement. CMS is actually in aggregate slower than the default GC configuration (Parallel GC), but it does provide smoother overall operation of the JVM.

What size (minor) GC and Full GC pauses are you seeing? The minor GC pauses typically occur every 1-10 seconds. The "real=N.NN" indicates when the JVM is collecting garbage and not executing Grinder threads. If say your GC is taking 200ms (real=0.2 secs) and minor GC is occurring every 1 second then 20% of your execution time is GC.

If it isn't GC, then you're going to have to collect some OS metrics to understand why Grinder isn't able to scale threads. I can't help you much with Windows other than to say the Java threading and process model is designed around a UNIX-like kernel and not a process-heavy Windows model.

If you're on LInux run:

man vmstat

Lots of docs in the vmstat manual page to understand how the JVM is interacting with your OS. Specifically you want less threads runnable than you have cores and generally no threads blocked. Also you want low system, I/O wait and interrupt CPU utilisation and no less than 20% CPU idle. Compare "vmstat 3" output between your 25 and 30 threads and try and determine what bottleneck you are hitting.

Regards,
Gary

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Re: Memory And Threads

Alex Bagehot
In reply to this post by Adil qureshi

Hi,

We probably need to cover some checks and get some more info:

What software versions grinder/java/etc is this?
Do you have the option of comparing the same on a Linux/other box?

What do you define as better performance?
How do you know it is not limited by the system under test?
What particular [work]load are you trying to achieve?

Answers to these questions may help progress it.

Thanks
Alex

On 31 Aug 2014 21:17, "Adil qureshi" <[hidden email]> wrote:
Hi Guys,

Greeting for the day.


I am getting better performance with 25 threads than 30 threads and the performance of grinder keeps on decreasing if I increase the number of threads.

The system from which I am running grinder is a Solaris server and has high CPU capability as well as RAM.

If I start more than one process and divide the threads among them the no of calls that grinder can make even decreases.

I am trying to achieve a particular load which has become impossible as of now  with threads so limited.


Any suggestions on this will be highly appreciated.

Thanks In Advance,

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Re: Memory And Threads

Marc Holden
In addition to what Gary and Alex have said, you need to take a close look at what the scripts are doing.

If the scripts are doing a lot of data processing, you may need to take a look at the size of the response objects being processed and the libraries being used.  From personal experience, the normal json processing libraries (org.json and/or simple json) used with jython are under achievers and tend to use a lot of CPU.  

It is also very beneficial to look at what the CPUs are doing.  Even though the average CPU usage may be low, you may see and individual core being pinned for long periods of time.  On a *nix system, you can do this from the top command by pressing the 1 character after starting top.  This will show the usage of each core.

Good luck!

-Marc





On Mon, Sep 1, 2014 at 2:47 AM, Alex Bagehot <[hidden email]> wrote:

Hi,

We probably need to cover some checks and get some more info:

What software versions grinder/java/etc is this?
Do you have the option of comparing the same on a Linux/other box?

What do you define as better performance?
How do you know it is not limited by the system under test?
What particular [work]load are you trying to achieve?

Answers to these questions may help progress it.

Thanks
Alex

On 31 Aug 2014 21:17, "Adil qureshi" <[hidden email]> wrote:
Hi Guys,

Greeting for the day.


I am getting better performance with 25 threads than 30 threads and the performance of grinder keeps on decreasing if I increase the number of threads.

The system from which I am running grinder is a Solaris server and has high CPU capability as well as RAM.

If I start more than one process and divide the threads among them the no of calls that grinder can make even decreases.

I am trying to achieve a particular load which has become impossible as of now  with threads so limited.


Any suggestions on this will be highly appreciated.

Thanks In Advance,

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