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From Miguel González Castaños <miguel_3_gonza...@yahoo.es>
Subject Re: heap memory issues
Date Mon, 18 Jun 2012 22:34:46 GMT
On 18/06/2012 09:52, Konstantin Kolinko wrote:
> 2012/6/16 Miguel González Castaños<miguel_3_gonzalez@yahoo.es>:
>> Dear all,
>>
>>    We have a webapp under Tomcat 5.5 and jdk 1.5 32 bits under a virtual
>> machine of 4 Gb and a 64 bits OS.
> 4 Gb is memory size?
Yes
>
>>    Some of you have helped me suggesting me to install Javamelody and sar to
>> monitor the system. Setting up heap dumps I have managed to see what was
>> going on with the eclipse memory analyzer.
>>
>>    The webapp sends emails that have been previously entered into the
>> database. It loads the emails into memory, so if you are sending 10k emails,
>> it loads 10k objects containing those emails. That makes the app to use
>> around 200-300 mb of the heap memory.
> Do you need to keep 10k of them in the memory at the same time?
> Usually one would send mails one by one and release their memory
> immediately.
I don't. Fortunately the developer has corrected this, so probably other 
issues will arise but not this one.
>
>
>>   The settings we have now for the JDK are:
>>
>>   CATALINA_OPTS="$CATALINA_OPTS -XX:+HeapDumpOnOutOfMemoryError
>> -XX:HeapDumpPath=/opt/tomcat5/logs/ -Xms128m -Xmx512m -verbose:gc
>> -XX:+PrintGCTimeStamps -XX:+PrintGCDetails"
>>
>>   Facts that I have witnessed:
>>
>>   If I try to increase the Xmx to 740m or 1024m the GC starts working very
>> much and Tomcat shuts down.
> GC? Or OS memory swapping?
GC, no swapping reported by sar.
>
>>   I have also tried downloading a 64 bits 1.7 jdk but I get the typical:
>>
>>   Java HotSpot(TM) 64-Bit Server VM warning: Exception
>> java.lang.OutOfMemoryError occurred dispatching signal SIGTERM to handler-
>> the VM may need to be forcibly terminated
> 64-bit JVM usually needs more memory than 32-bit one,  because memory
> address range is wider and pointers need more memory.
I know, but how do I know how much ram to assign in a 64 bits jdk? We 
are planning to move to a bigger server (hopefully 16 or 32 gb).

Miguel

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