Re: when to use hugepages

  • From: Riyaj Shamsudeen <riyaj.shamsudeen@xxxxxxxxx>
  • To: guillermo.bort@xxxxxxx
  • Date: Mon, 20 Oct 2008 09:45:11 -0500

Hi bort

I just resolved a major performance issue using hugepages, at a client site. IMHO, only reason I can think of, not using hugepages is that you are really low on free memory & you have other memory hungry applications in that server and you don\t want to lock SGA in memory. pagetables size will be a good indicator to show how much memory is wasted.

It is easy to prove your point. In test server, create a condition such that free memory is depleted. When kscand/kswapd wakes up freeing up memory, they will page some part of SGA also. Performance issue will be visible :-). Run a script in the background capturing per minute execution time.

Then, setup hugepages, create same conditions and see how performance is.

As long as, you make sure that databases is indeed using hugepages, it is an excellent choice.

The Pythian Group

Bort, Guillermo wrote:

Hi all,

After the thread about hugepages a while ago I became interested in them, and told the SA about them. He said it’s viable in most of our environments, so it now lies with me to decide where to use hugepages. As I have no experience with this, I’d very much appreciate any pointers as to how to decide whether to use hugepages or not in a given environment. Also, if you know of a way to ‘benchmark’ de performance to have something to show the customer (as the change would require some downtime). I think it goes without saying that this will be tested in (redundantly enough) testing and QA environments way before we even consider trying it in pre-productive and productive environmets.

Thanks in advanced

*Guillermo Alan Bort*

DBA / DBA Main Team

*EDS*, an HP company


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