--- Nelson Minar <[EMAIL PROTECTED]> wrote:
>
> >Essentially, RSS reflects how much of the program's address space
> has
> >been touched recently, as well as the kernel's decision about how
> to
> >allocate physical memory among processes that need it.
>
> Yes, the RSS is the most useful number. The VSZ for a Java process
> is
> just going to be the maximum heap. Ie: you run "java -mx128M", and
> VSZ
> will be 128M.
But that's not the case - at least not on my Linux 2.2.12 system
with Blackdown 1.2preV2.
I understand what RSS is, and what the 'SIZE' column should be -
the virtual memory size. And I also would have thought that the
latter would be the total amount of memory that java grabs at the
beginning (just like 'ps' reports). But I've found that *both*
SIZE and RSS vary as the java program uses and releases memory.
I do a System.gc() and the SIZE will drop from 140Mb down to
about 50Mb (with RSS following suit, to be <= SIZE, of course).
Can I ask a couple of other memory related questions? My
java application prints a number of pages of output, doing
drawImages() of a number of images per page - memory used
increases dramatically. At the end of the print process all
the Image objects are released, yet the memory-used doesn't
drop at all - I have to do an explicit gc(). When does java's
normal garbage collection cycle kick in? I wait a couple of
minutes but it doesn't reduce memory of its own accord.
The application has a menu option which does a System.gc() so I
can explicitly initiate collection. I click on it once, and
the SIZE/RSS go from 140+Mb down to about 80Mb. I click on it again,
and it drops to 60-odd. I click on it again, we're down to 50Mb,
etc.
What are the mechanics of garbage collection? I would have thought
that a single pass would free up everything that isn't referenced.
Thanks,
Brad Rosser
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