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From evebill8 <>
Subject Re: Heap size rule for Tomcat 5.5
Date Sat, 06 Feb 2010 17:45:04 GMT

Got it!  My app is very read intensive so I try to cache lots of objects into
the RAM.  Therefore, I like to allocate more RAM to the heap since RAM is
cheap now.  Thanks for your advise!


Peter Crowther wrote:
> On 5 February 2010 18:05, evebill8 <> wrote:
>> Cool!  I just want to confirm if the rule is right.  My IT guy also does
>> not
>> believe it.
>> It wasn't a bad rule of thumb as a place from which to start tuning when
> typical server memory sizes were 0.5G to 2G - it reserved "sort-of enough"
> RAM for the OS and the non-heap parts of Java and "sort-of enough" RAM for
> the web application, though as you can imagine that varied quite a lot. 
> But
> it could never really be said to be optimal, and ideally you'd always
> measure and tune.
> These days, there's so much more RAM in most servers that tuning becomes
> more relevant if the load's high.  If your application is very heavy on
> disk
> reads, for example, you might do better to reduce its heap size in order
> to
> give the OS more space to cache disk pages.  By contrast, I have one
> *very*
> heavy compute application (not directly a web app) that likes all the RAM
> it
> can get as heap memory to cache intermediate results in case they can be
> re-used.
> - Peter

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