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Posted to users@tomcat.apache.org by MW Janssen <ma...@bedrijven.nl> on 2006/09/12 15:59:17 UTC
question about PS Old Gen memoy
Hello all,
I am reading a lot on JVM garbage collection tuning but i cant figure out
what the best situation is for me. I run a very large application without
any problems except one remarks.
I see (i am using lambda probe) that my old generation memory is growing
until the 70% (is default I read) of my total heap size. My xmx and xms
parameters are both 1024m. So the olg generation take about 700 mb.
The jvm (default jvm) doesn't automatically garbage collect the olg gen
space memeory. So this looks like a memory leak, however if I explicit do a
gc() all the old gen memory is released, so i dont think its a memory leak.
How can I avoid (the best solution) that the old gen is filling until 70% of
the total memory allocation by the jvm and what causes this? Could lampda
probe cause this?
Thx in advanced.
ps. I added a screenshot of my memeory allocation (in lambda probe)
Maarten Janssen
RE: question about PS Old Gen memoy
Posted by "Caldarale, Charles R" <Ch...@unisys.com>.
> From: MW Janssen [mailto:maarten@bedrijven.nl]
> Subject: RE: question about PS Old Gen memoy
>
> So no need to do anything and not to worry that I ran out
> of memory..thats what you saying..right?
> And a full GC is only done by the JVM as its really needed?
Correct on both accounts (with allowances for English not being your
primary language - should be "will run out" rather than "ran out"; if
you actually do run out of memory, you'll get the appropriate
exception).
This paper has some interesting content:
http://java.sun.com/docs/hotspot/gc5.0/gc_tuning_5.html
This tool may also be of interest:
http://java.sun.com/developer/technicalArticles/Programming/GCPortal/ind
ex.html
- Chuck
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RE: question about PS Old Gen memoy
Posted by MW Janssen <ma...@bedrijven.nl>.
No i have no evidence...i was only guessing. So no need to do anything and
not to worry that I ran out of memory..thats what you saying..right?
And a full GC is only done by the JVM as its really needed? and in this case
it isnt you say..am i right?
thxfor your quick response!
Regards,
Maarten Janssen
-----Oorspronkelijk bericht-----
Van: Caldarale, Charles R [mailto:Chuck.Caldarale@unisys.com]
Verzonden: dinsdag 12 september 2006 16:48
Aan: Tomcat Users List
Onderwerp: RE: question about PS Old Gen memoy
> From: MW Janssen [mailto:maarten@bedrijven.nl]
> Subject: RE: question about PS Old Gen memoy
>
> Because I think the old gen is still filled also the 70% is reached.
So what? Again, that's how it's designed to work. Collecting the young gen
is much cheaper than doing the old gen, so there are many small collections
performed before attempting a big one. The old gen steadily accumulates
objects until the full gen is invoked.
> The jvm will do a garbage collect to free up memory for the old gen so
> i think there will be more and more garbage collections to achieve the
> 70%.
I have no idea what the above sentence was trying to convey.
Do you have any evidence that the current behavior is somehow impacting the
performance or reliability of your applications?
- Chuck
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RE: question about PS Old Gen memoy
Posted by "Caldarale, Charles R" <Ch...@unisys.com>.
> From: MW Janssen [mailto:maarten@bedrijven.nl]
> Subject: RE: question about PS Old Gen memoy
>
> Because I think the old gen is still filled also the 70%
> is reached.
So what? Again, that's how it's designed to work. Collecting the young
gen is much cheaper than doing the old gen, so there are many small
collections performed before attempting a big one. The old gen steadily
accumulates objects until the full gen is invoked.
> The jvm will do a garbage collect to free up memory for
> the old gen so i think there will be more and more garbage
> collections to achieve the 70%.
I have no idea what the above sentence was trying to convey.
Do you have any evidence that the current behavior is somehow impacting
the performance or reliability of your applications?
- Chuck
THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY
MATERIAL and is thus for use only by the intended recipient. If you
received this in error, please contact the sender and delete the e-mail
and its attachments from all computers.
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RE: question about PS Old Gen memoy
Posted by MW Janssen <ma...@bedrijven.nl>.
He Chuck,
Because I think the old gen is still filled also the 70% is reached. The jvm
will do a garbage collect to free up memory for the old gen so i think there
will be more and more garbage collections to achieve the 70%. I think there
also a lot of unused stuff in the old gen (otherwise a full gc() wont
release that much) that can be cleared so that I have more memory left.
Kind regards
Maarten
-----Oorspronkelijk bericht-----
Van: Caldarale, Charles R [mailto:Chuck.Caldarale@unisys.com]
Verzonden: dinsdag 12 september 2006 16:05
Aan: Tomcat Users List
Onderwerp: RE: question about PS Old Gen memoy
> From: MW Janssen [mailto:maarten@bedrijven.nl]
> Subject: question about PS Old Gen memoy
>
> How can I avoid (the best solution) that the old gen is filling until
> 70% of the total memory allocation by the jvm and what causes this?
Why do you think this is a problem? This is how the HotSpot GC is designed
to work. A full GC - one that collects the old gen - is not done until
absolutely necessary or an explicit call to gc() is made.
- Chuck
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RE: question about PS Old Gen memoy
Posted by "Caldarale, Charles R" <Ch...@unisys.com>.
> From: MW Janssen [mailto:maarten@bedrijven.nl]
> Subject: question about PS Old Gen memoy
>
> How can I avoid (the best solution) that the old gen is
> filling until 70% of the total memory allocation by the jvm
> and what causes this?
Why do you think this is a problem? This is how the HotSpot GC is
designed to work. A full GC - one that collects the old gen - is not
done until absolutely necessary or an explicit call to gc() is made.
- Chuck
THIS COMMUNICATION MAY CONTAIN CONFIDENTIAL AND/OR OTHERWISE PROPRIETARY
MATERIAL and is thus for use only by the intended recipient. If you
received this in error, please contact the sender and delete the e-mail
and its attachments from all computers.
---------------------------------------------------------------------
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