Re: Linux max on shared buffers?

Curt Sampson wrote:
> On Wed, 10 Jul 2002, Bruce Momjian wrote:
>
> > Woh, 10MB is clearly too low.  Remember, there is copying overhead of
> > moving data from the kernel to the PostgreSQL shared buffers.
>
> Yes, but the cost of copying between a postgres buffer and an OS buffer
> is much, much less than the cost of copying between an OS buffer and disk.
>
> However, it all depends on your working set, doesn't it? So I can't make
> a strong argument either way. What do you think is better? 20 MB? 100
> MB? Do you allocate based on the number of connections, or a proportion
> of the machine's memory, or something else? I was estimating based on
> the number of connections.
>

If it is a dedicated machine, I would think some percentage of total RAM
would be good, perhaps 25%.  If it isn't dedicated, the working set
becomes a major issue, yes.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026