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use_large_pages parameter and AMM [message #517949] Fri, 29 July 2011 11:59 Go to next message
John Watson
Messages: 4865
Registered: January 2010
Location: Global Village
Senior Member
It always used to be that Automatic Memory Management and Linux huge pages were incompatible: you had to use one or the other. But 11.2.0.2 has new parameter, USE_LARGE_PAGES. This isn't documented apart from a few articles on metalink, but Googling it suggests that if it is on TRUE (the default) or ONLY then I can use AMM with huge pages.

Is anyone doing this on Linux? And will it have any effect on other operating systems?

Thanks for any insight.

[update: typo]

[Updated on: Fri, 29 July 2011 12:02]

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Re: use_large_pages parameter and AMM [message #518011 is a reply to message #517949] Sun, 31 July 2011 06:48 Go to previous messageGo to next message
John Watson
Messages: 4865
Registered: January 2010
Location: Global Village
Senior Member
Replying to myself...
Do people have experience of large pages on Solaris? I have this article from the OS side
http://www.solarisinternals.com/wiki/index.php/Multiple_Page_Size_Support
and this from the DB side
http://developers.sun.com/solaris/docs/solaris-sparc-061110.pdf
They are largely pre-Solaris 2.10 and pre-T3 architecture, but they suggest that large pages are a Good Thing. Neither mentions use_large_pages.
This tells me what is possible, and what I have by default:
$ pagesize -a     
8192
65536
524288
4194304
$ pagesize
8192

(ps - anyone tried AMM and Linux huge pages?)
Re: use_large_pages parameter and AMM [message #518737 is a reply to message #518011] Fri, 05 August 2011 15:50 Go to previous messageGo to next message
John Watson
Messages: 4865
Registered: January 2010
Location: Global Village
Senior Member
My second reply to myself.

As far as I can see, all the web references that say AMM and Huge Pages can be used together come from this one web article:

http://abiliusta.blogspot.com/2011/04/huge-pages-and-amm-is-possible-and.html

Following some research, this article appears to be a total mis-understanding of the use_large_pages parameter. The parameter does not permit use of huge pages. Its purpose is to force an error if huge pages are not available, rather than letting Oracle revert silently to non-huge pages.

Sorry I publicised this mistake. According to Oracle Corp, AMM and huge pages are incompatible. And that's it.
Re: use_large_pages parameter and AMM [message #518749 is a reply to message #518737] Sat, 06 August 2011 01:39 Go to previous message
Michel Cadot
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Registered: March 2007
Location: Nanterre, France, http://...
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Quote:
Sorry I publicised this mistake.

Don't be sorry, this topic is very interesting and, in the end, gives a clear answer on the issue.

Thanks
Michel
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