Re: Warm-up cache may have its virtue

Qingqing Zhou <zhouqq(at)cs(dot)toronto(dot)edu> writes:
> Hinted by this thread:
> http://archives.postgresql.org/pgsql-performance/2006-01/msg00016.php
> I wonder if we should really implement file-system-cache-warmup strategy
> which we have discussed before.

The difference between the cached and non-cached states is that the
kernel has seen fit to remove those pages from its cache. It is
reasonable to suppose that it did so because there was a more immediate
use for the memory. Trying to override that behavior will therefore
result in de-optimizing the global performance of the machine.

If the machine is actually dedicated to Postgres, I'd expect disk pages
to stay in cache without our taking any heroic measures to keep them
there. If they don't, that's a matter for kernel configuration tuning,
not "warmup" processes.

regards, tom lane