Re: [HACKERS] Postgres Performance

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@doc.mssm.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
> 
> ************