Using large pages to eliminate TLB misses has nothing to do with the
size of the objects. From the view of the operating system java heap is
just a huge and continuous chunk of memory. Anything what's inside is
managed by the JVM. But whenever the JVM needs to access an adress it
needs to make an address calculation as described in the article. Once
the needed adress translation tables do not fit into the TLB,
performance gets bad. Since Java often uses a large and continuous heap
it's a very good candidate for using large pages, saving entries in the TLB.
Leon Rosenberg wrote:
Hi,
recently I found (ok actually our sysadmin did) this articles on the
web, and wanted to share some thoughts.
http://www.devx.com/amd/Article/30529
http://www.devx.com/amd/Article/30785
The article describes, that using opteron and large memory pages can
give significant performance wins. I don't doubt this, but I doubt,
that large memory pages are a real use case in the tomcat / java
webapps world. At least in applications I saw there are always many
small objects, tags, beans, dtos.
any other thoughts?
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