| From: | "Scott Marlowe" <smarlowe(at)qwest(dot)net> |
|---|---|
| To: | "Ioannis Theoharis" <theohari(at)ics(dot)forth(dot)gr> |
| Cc: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: Page Miss Hits |
| Date: | 2004-08-02 16:19:27 |
| Message-ID: | 1091463567.27166.44.camel@localhost.localdomain |
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| Thread: | |
| Lists: | pgsql-performance |
On Mon, 2004-08-02 at 02:11, Ioannis Theoharis wrote:
> Hi, i would like to answer if there is any way in postgres to find the
> page miss hits caused during a query execution.
>
>
> Is there something like explain analyze with the page miss hits???
You're making a basic assumption that is (at least currently) untrue,
and that is that PostgreSQL has it's own cache. It doesn't. It has a
buffer that drops buffer back into the free pool when the last
referencing backend concludes and shuts down. So, PostgreSQL currently
relies on the kernel to cache for it. So, what you need is a tool that
monitors the kernel cache usage and its hit rate. I'm not familiar with
any, but I'm sure something out there likely does that.
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