After my recent blog entry entitled Configuring Linux Hugepages for Oracle Is Just Too Difficult! Isnt It? Part I, I engaged in a couple of email threads and a thread on oracle-l about when to employ hugepages. In those exchanges I was amazed to find that it is still a borderline issue for folks. I feel it is very cut and dried and thus I prepared the following guidelines that more or less spell it out.
To make the point of how urgently Oracle DBAs need to qualify their situation against list items 1.1 through 1.3 above, please consider the following quote from an internal email I received. The email is real and the screen output came from a real customer system. Yes, 120+ gigabytes of memory wasted in page tables. Fact is often stranger than fiction!
And here is an example of kernel pagetables usage, with a 24GB SGA, and 6000+ connections .. with no hugepages in use ..
# grep PageT /proc/meminfo
PageTables: 123731372 kB
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