Re: Session timeout and memory
Re: Session timeout and memory
- Subject: Re: Session timeout and memory
- From: Chuck Hill <email@hidden>
- Date: Wed, 13 Sep 2006 07:46:52 -0700
What you are seeing is almost certainly just the way garbage
collection works. When the session times out, the objects it
allocated are available for garbage collection. They are not
collected at that time, just made available for collection. The
garbage collector won't run until it needs to.
Chuck
On Sep 11, 2006, at 11:18 PM, Ute Hoffmann wrote:
Ok, perhaps I'm looking at the wrong thing. This is the piece of
code which I use to determine the used memory:
Runtime runtime = Runtime.getRuntime();
double nochVoranden = new Double(runtime.totalMemory () -
runtime.freeMemory ()).doubleValue();
So this happens to the logs:
The memory goes up inside of the session. It sometimes drops a bit
but it mainly goes up. So there seems to be a memory leak somewhere...
Ok, but then the session is terminated or times out. So I would
assume that then the memory is returned as free memory.
So the next session should again show used memory lets say 6 MB.
But when the previous session had a used memory of lets say 50 MB
the next session (created well after the first session is timed out
or terminated) will show 50MB + of used memory.
And yes: There was only one session present in the testcase and it
clearly went up after the first session was timed out without
releasing this used memory.
Do I have to schedule the instances to get rid of this (as it
happens by design) or does it point me to a memory leak in my code
which means whatever holds the memory cannot be released even after
the session is terminated.
Regards
Ute
Anfang der weitergeleiteten E-Mail:
Von: Q <email@hidden>
Datum: Di, 12. Sep 2006 01:43:35 Europe/Berlin
An: Chuck Hill <email@hidden>
Cc: Ute Hoffmann <email@hidden>, webobjects-
email@hidden
Betreff: Re: Session timeout and memory
On 12/09/2006, at 2:26 AM, Chuck Hill wrote:
In addition to garbage collection which has been mentioned, be
careful of what you are looking at. If additional memory is
allocated to the JVM process, it will not be returned to the
operating system until the JVM process terminates. In other
words, the total heap size will never decrease but free memory on
the heap will vary as objects are created and the garbage
collector runs.
Chuck
It should also be pointed out that this is a good thing not a
liability that needs special consideration, because it means that
the JVM doesn't need to constantly malloc and free memory.
Provided there isn't an actual leak causing the JVM size to
continually grow unexpectedly, the virtual memory allocation
shouldn't be something to really worry about, as any vm pages that
go unused for long enough will eventually get paged out by the OS
should the physical memory be required for something else.
Assuming your OS has got enough swap allocated.
--
Seeya...Q
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