On 7/9/2004 10:16 AM, Merlin Moncure wrote:

What is it about the buffer cache that makes it so unhappy being able
hold everything? I don't want to be seen as a cache hit fascist, but
it just better if the data is just *there*, available in the
address space ready for each backend process to access it, rather than
expecting the Linux cache mechanism, optimised as it may be, to have
to do
the caching?

The disk cache on most operating systems is optimized. Plus, keeping shared buffers low gives you more room to bump up the sort memory, which will make your big queries run faster.

Plus, the situation will change dramatically with 7.5 where the disk cache will have less information than the PG shared buffers, which will become sequential scan resistant and will know that a block was pulled in on behalf of vacuum and not because the regular database access pattern required it.


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