Re: Lockless pg_buffercache - Mailing list pgsql-general

From Scott Marlowe
Subject Re: Lockless pg_buffercache
Date
Msg-id dcc563d10802100139n5f92062eg152c63628828ef1@mail.gmail.com
Whole thread Raw
In response to Lockless pg_buffercache  ("Markus Bertheau" <mbertheau.pg@googlemail.com>)
Responses Re: Lockless pg_buffercache
List pgsql-general
On Feb 9, 2008 10:34 PM, Markus Bertheau <mbertheau.pg@googlemail.com> wrote:
> Hi,
>
> I want to use the pg_buffercache contrib module for monitoring our
> server. It takes a lock on all buffers and then on each buffer header
> in order to get a consistent picture of the buffers. I would be
> running the function provided by the module once every 5 minutes.

If it takes 500mS every 5 minutes that might be an acceptable decrease
in performance for that second or two.

> I'm worrying about the performance hit of that - a comment in the code
> says it's horrible for concurrency.

It is, but again, it really depends on the time frame etc.  If you can
run it quickly as a series of related queries or a user function, it
should be fast enough to not be a significant burden.

So, what's the real burden like from the pg_buffercache contrib module?

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