Re: The black art of postgresql.conf tweaking

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Josh Berkus wrote:

| Paul,
|
|
|>>Physical Memory: 2077264 kB
|
|
|>>sort_mem = 12000
|
|
| Hmmm.  Someone may already have mentioned this, but that looks problematic.
| You're allowing up to 12MB per sort, and up to 300 connections.  Even if each
| concurrent connection averages only one sort (and they can use more) that's
| 3600MB ... roughly 1.5 times your *total* RAM, leaving out RAM for Apache,
| postmaster, shared buffers, etc.
|
| I strongly suggest that you either decrease your total connections or your
| sort_mem, or both.

Of course your are speaking about the "worst case", I aplly in scenarios like
this on the rule 80/20: 80% of connection will perform a sort and 20% will allocate
memory for the sort operation in the same window time:

300 -- 80% -->  240 --> 20% --> 48


48 * 12MB = 576 MB

that seems resonable with the total ammount of memory available.

Am I too optimistic?



Regards
Gaetano Mendola

















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