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From "Mark H. Wood" <mw...@IUPUI.Edu>
Subject Re: Xmx and Xms size
Date Wed, 30 Jan 2008 14:36:41 GMT
What kind of processors specifically?  In a 32-bit address space,
there's no point in giving Tomcat more than 2GB, because the JVM won't
use it.  If you have 64-bit userspace and a JVM built for it then you
can use more, but remember to leave a bit for OS caches, other
processes, etc.  (Starve the block cache and your disk I/O throughput
will suffer.)

From somewhere I recall a rule of thumb: if the box's primary duty is
to run a single Java app., give that app. up to 75% of physical
memory.  But that's a rule of thumb, and could be made nonsense by
unusual hardware or an unusual app.  Any answer you get here should be
taken as initial conditions for a tuning exercise: start there,
measure performance and resource utilization, theorize, adjust, repeat
until you get the performance you need or are convinced that you can't
without changing something else (application design, bigger/faster
hardware, network optimization, whatever).

Mark H. Wood, Lead System Programmer   mwood@IUPUI.Edu
Typically when a software vendor says that a product is "intuitive" he
means the exact opposite.

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