> What is it about the buffer cache that makes it so unhappy being able to
> hold everything? I don't want to be seen as a cache hit fascist, but isn't
> it just better if the data is just *there*, available in the postmaster's
> 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?
Because the PostgreSQL buffer management algorithms are pitiful compared
to Linux's. In 7.5, it's improved with the new ARC algorithm, but still
- the Linux disk buffer cache will be very fast.
Chris
