> > 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.

FreeBSD, IRIX, and AIX, implement it, and ... *smiles with pride*
looks like Linux does too given the number of security vulnerabilities
associated with the call.  :-]


Sean Chittenden

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