Re: Experiences & recommendations related to HUGEPAGES in RHEL 7
- From: Mladen Gogala <gogala.mladen@xxxxxxxxx>
- To: Dba DBA <oracledbaquestions@xxxxxxxxx>
- Date: Sat, 15 Jul 2017 23:37:56 -0400
On Sat, 15 Jul 2017 12:27:04 -0400
Dba DBA <oracledbaquestions@xxxxxxxxx> wrote:
We use huge pages here as a standard. How do people test huge pages to
isolate variables so you can measure the improvement from huge pages?
Basically, huge pages should result in less time being spent in kernel mode.
The only real consequences of huge pages are smaller page tables and SGA not
being handled by swapper and page stealing daemon. In case of virtual machines,
paging is even more expensive, so smaller page tables are even more
You are allocating the same amount of memory either using 4K pages or using 2M
pages. The only real difference is the amount of overhead work that system has
to perform on this memory. And in case of huge pages, that overhead is few
percents lower than in the case of the 4K pages. That's about it. It's nothing
spectacular, it's not a "turbo" button. You will not turn on the afterburner by
using huge pages.
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