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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