Sean Chittenden wrote:
> Nor could it ever be a win unless the cache was populated via
> O_DIRECT, actually.  Big PG cache == 2 extra copies of data, once in
> the kernel and once in PG.  Doing caching at the kernel level, however
> means only one copy of data (for the most part).  Only problem with
> this being that it's not always that easy or an option to reconfig a
> kernel to have a bigger FS cache.  That said, tripple copying a chunk
> of mem is generally faster than even a single disk read.  If
> PostgreSQL ever wanted to have a platform agnostic way of doing
> efficient caching, it'd likely have to be in the userland and would
> require the use of O_DIRECT.

Actually, I think of O_DIRECT as platform-dependent.

  Bruce Momjian                        |
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