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From Andy Dawson <a...@iti.upv.es>
Subject Re: Monitor Results - Memory Load Percentage
Date Fri, 21 Jul 2006 08:46:50 GMT
Hi Peter,

As always thanks for your reply.

I assumed there was a good reason for the choice - I did google before 
posing the question, is there a more appropriate search that might 
prevent (my) duplicate questions? My more detailed search just now 
pulled up your blog on the topic.

The application that I am load testing keeps dropping out unexpectedly 
over time, I was finding that a reported memory % that continually 
bounces around 90% from beginning to the end of a test with steadily 
increasing number of threads (end being when the server stops 
responding), didn´t tell me what I expected, hence the change to my 
local set up.

I deduce I should investigate using a profiler rather than tweaking the 
monitor and getting (potentially) erroneous or misleading results (due 
to local changes).

Thanks & regards,

Andy

Peter Lin wrote:
> The reason for using (total - free)/total is that max value is not 
> accurate.
> the only cases where max is more useful is if someone wants to know how
> close to Max they are and they've set an explicit Max heap.
>
> other people have asked about this in the past. For example, on linux or
> solaris, if one were to use top to see the memory used by tomcat, 
> often it
> won't match the max value. Therefore it's not accurate and doesn't really
> help.
>
> tomcat could crash before ever reaching the max. Most of the cases 
> where I
> see servlet container crash is a sudden spike, which ends up looking 
> like a
> spike in jmeter tomcat monitor.  hopefully that explains the rationale
> behind using (total - free)/total
>
> peter
>
>
>
> On 7/20/06, Andy Dawson <andy@iti.upv.es> wrote:
>>
>> Hi All,
>>
>> I have a simple jsp application I am currently testing and Tomcat is
>> installed with all the defaults. After noticing that the memory load was
>> always above 50% according to JMeter I wondered if this was reporting
>> what I was expecting.
>>
>> With the defaults, and for low/no load, the server reports something 
>> like:
>> Free Memory: 13300000
>> Total Memory: 32000000
>> Max Memory: 66600000
>>
>> The documentation implies, as is clear from the code, that the memory
>> load percentage is calculated as
>> Load = (Total - Free)/Total
>>
>> I was expecting it to be:
>> Load = (Total - Free)/Max
>>
>> Do I understand correctly the intended meaning of server Memory Load?
>>
>> Thanks in advance, Regards,
>>
>> Andy
>> PS. I´ve already changed the code in my install to do the above.
>> Ref:
>> http://jakarta.apache.org/jmeter/usermanual/build-monitor-test-plan.html
>>
>>
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>>
>


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