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Re: Memory allocation jump after running for a while with a largenumber of threads



On Wed, 19 Feb 2003, Hui Huang wrote:

> What's interesting are numerous 992K map'ed memory regions (Note there
> is a 1M hole between every 992K chunk and the next 32K):
> 
> [...]
> bdf00000 (32 KB)       rw-p (00:00 0)
> bdf08000 (992 KB)      ---p (00:00 0)

there might be another effect. If this is the thread stack (is it?), then
Linux will lazy-allocate the pages mapped by it, and NPTL will cycle the
stacks (ie. instead of munmap()-ing them, they get cached). I dont
remember the exact tresholds NPTL is using for caching stacks. In any
case, the RSS of the JVM process/threads should show the exact amount of
memory allocated.

if you add up the memory maps of the JVM, how much RAM is it, and how big
is the RSS [in the 'good' and in the 'bad' cases]?

	Ingo






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