Re: Using a certain percentage of the JVM storage

From:

Eric Sosman <Eric.Sosman@sun.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 17 Sep 2008 11:29:05 -0400

Message-ID:

<1221665245.418073@news1nwk>

Stefan Ram wrote:

  An appliation should use a certain percentage (approximately)
  of the data storage area of its JVM for output file buffers.
  If the buffers ever hold more data than this, they are to be
  flushed to their respective files. The buffer size should not
  be fixed, so that when the user calls the JVM on the command
  line with a large maximum memory size, the application will
  use it, or when a small memory size is specified, the
  application will still run.

  Is there a best practice to achieve this?

IMHO the best practice might be not to try. A package that
treats the whole system (the whole JVM, in this case) as its own
private playground is unlikely to "play well with others." Even
if the package plays alone, extravagant memory use may lead to
more GC activity than you'd like.

But if you're convinced it's the right thing to do, I'd say
the methods of Runtime are the place to start. Subtract freeMemory()
from totalMemory() to estimate "memory in use," and subtract that
from maxMemory() to estimate "memory potentially available." Deduct
a fudge factor for classes yet to be loaded and objects yet to be
created, and use some percentage of the result.

--
Eric.Sosman@sun.com