RE: Question about SGA memory allocation and sizing
- From: Austin Hackett <hacketta_57@xxxxxx>
- To: "Oracle-L@xxxxxxxxxxxxx" <Oracle-L@xxxxxxxxxxxxx>
- Date: Thu, 06 Sep 2012 11:56:49 +0100
Hi Peter
Apologies in advance if what I'm about to mention isn't news to you!
With a massive SGA, no huge pages, and lots of concurrently active
sessions, the amount of memory used for the page table might be enough
to topple the server via a swap storm. For instance, I have seen a
system with a 40 or so GB buffer cache and 22GB of memory being used
for page tables. There is a great presentation that shows you how to
calculate page table memory usage based on the number of processes and
the size of your SGA:
http://www.pythian.com/news/741/pythian-goodies-free-memory-swap-oracle-and-everything
. grep PageT /proc/meminfo will show you how much memory is used for
the page table. I'd probably be tempted to crank your memory target
right down and avoid the possibility of "a perfect storm" (where
oracle is using all the allowed memory and lots of processes are
active) until you get can get HugePages implemented.
Hope that helps
Austin
--
//www.freelists.org/webpage/oracle-l
Other related posts:
