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From Rainer Jung <rainer.j...@kippdata.de>
Subject Re: Tomcat and HugeTLB best practices for a 16GB machine
Date Mon, 03 Mar 2008 23:03:24 GMT
Google with java tlb gives an interesting first hit, a recent 
presentation from an Intel guy about joint Sun/Intel work:

http://guermonprez.eu/paul/blog/public/images/voyage/sun_tech_days_2007/intel_java_sun_tech_days.pdf

 From what he writes, I guess he's mostly talking about Java 6. So don't 
take everything as given if you need to work with an older JVM.

There is one slide about Windows and one about Linux in the presentation 
with some technical details about enabling large page support. According 
to this document, you only get 4MB page support though. It's much better 
than the default 4 or 8KB page size, but since there are only 64 entries 
with a reasonably big heap you still get tlb misses. Of course much less 
than with the default size. More recent Sparc processors support 256MB 
page size.

Some Info is also on

http://java.sun.com/javase/technologies/hotspot/largememory.jsp

Concerning mx and ms: Once you know, how much memory you need, setting 
the equal will allocate one large chunk of memory during jvm startup, so 
chances are good, that you will use the TLB efficiently.

1.6.0 source also contains info on the following switches:

bool  UseLargePages               -
     "Use large page memory"
uintx LargePageSizeInBytes        0
     "Large page size (0 to let VM choose the page size"
uintx LargePageHeapSizeThreshold 128*M
     "Use large pages if max heap is at least this big"

Regards,

Rainer

Derek Fedel schrieb:
> Hi all,
> 
> I was wondering if anyone has played around with Tomcat and HugeTLB
> support on anything similar to the following hardware/software setup:
> 
> * 2x Dual Core Xeon
> * 16 GB Ram
> * ISCSI attached root disks (Gentoo Linux based)
> 
> If so, does anyone have any recommendations on how to go about tuning
> it to get the most "bang for the buck" so to speak? General HugeTLB
> related info would be helpful too, any ideas for figuring out the
> optimal settings, etc. I've read pretty much every bit of info I can
> on this thats Googlable, and I don't really see any information
> related to what (if anything) -Xms and -Xmx should be set to either,
> so if anyone has any suggestions there I'd be eternally grateful. :)
> 
> 
> Thanks!
> Derek

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