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Re: [HACKERS] Postgres Performance

From: Edwin Ramirez <ramirez(at)doc(dot)mssm(dot)edu>
To: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] Postgres Performance
Date: 1999-09-08 21:05:38
Message-ID: 37D6CFA2.94AA5B38@doc.mssm.edu (view raw or flat)
Thread:
Lists: pgsql-hackers
If I do a large search the first time is about three times slower than
any subsequent overlapping (same data) searches.  I would like to always
get the higher performance. 

How are the buffers that I specify to the postmaster used?
Will increasing this number improve things?

The issue that I am encountering is that no matter how much memory I
have on a computer, the performance is not improving.  I am willing to
fund a project to implement a postgres specific, user configurable
cache.

Any ideas?
-Edwin S. Ramirez-

Tom Lane wrote:
> 
> Edwin Ramirez <ramirez(at)doc(dot)mssm(dot)edu> writes:
> > I have a couple of large(?) tables which I would like to keep them in
> > memory (cached) so that searches are performed as fast as possible.
> > Is it possible to 'pin' the tables and it's indexes in memory?
> 
> If the tables are being touched often, then they will stay in buffer
> cache of their own accord.  I doubt that pinning them would improve
> performance --- if they do get swapped out it'd be because some other
> table(s) need to be accessed now, and if you did have these tables
> pinned you'd be taking a large hit in access performance for those other
> tables because of inadequate buffer space.  LRU buffering policy really
> works pretty well, so I don't think you need to worry about it.
> 
> > currently I run the postmaster with the following setting:
> >       postmaster -i -B 2048 -o '-S 2048'
> > Are there any other options/values which would yield better performance?
> 
> If you have a reliable OS and power source, consider -o -F (no fsync).
> This usually makes for a very substantial performance improvement, and
> it can only hurt if your machine goes down without having performed
> all the writes the kernel was told to do.
> 
>                         regards, tom lane
> 
> ************

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