[4060] in java-interest
memory allocation pool size
daemon@ATHENA.MIT.EDU (Larry Lam)
Fri Dec 8 16:46:08 1995
Date: Fri, 8 Dec 1995 11:59:55 -0800
From: Larry.W.Lam@Eng.Sun.COM (Larry Lam)
To: java-interest@java.Eng.Sun.COM
Hi all:
I have a relatively small standalone program that create a lot of
small objects and I keep getting "OutOfMemeoryError" error.
I increase the memory allocation pool increment of 4Mb (using -mx
option in java), and finally the program was able to complete
with "-mx64m".
Here is the semi-pseudocode of the program:
for (int i = 0; i < 1700; i++) {
create a Hashtable
create 200 objects (100 keys and their associated value)
store the objects (keys and values) into hashtable
save the hashtable
// just in case...
run garbage collection every 100 interations
}
At the end of this code segement, there are ~340,000 objects stored
in 1700 hashtables.
Now, here is the puzzle. When I increse the size of the objects, (they
can be totaled to ~20MB increase in size), the new program was able to
complete with the same size of memory pool ("-mx64m")!! Any logical
explanation?
In general, is there any way to estimate memory usage of a java program?
It would be nice to know the size of a object reference and memory
overhead for each object so one can preallocate enough memory.
Any information would be appreciated.
larry lam
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