Forum OpenACS Q&A: Re: Re: Performance Problems - what is the bottleneck?

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Posted by Steve Manning on
In PG, increase:
shared_buffers = 65636
sort_mem = 32168

I would be careful of setting shared_buffers so high. Several Pg tuning articles suggest that this can cause performance degradation. Its not a straight forward calculation however so testing different values might be worthwhile. Setting shared_buffers to about 6% of memory (about 31457 on a 4Gb machine) should be starting point especially when used in conjunction with effective_cache_size set to a decent value.

A decent effective_cache_size allows the query planner to uses indexes instead of sequential scans. On a mchine dedicated to Pg this value can be set very high between 2/3 and 3/4 of RAM seems to be the suggestion - Nima has this set to 786432 which equates to 6Gb - might be a tad high on a 4Gb machine. Again experimentation to find a good value seems to be the order of the day.

- Steve