On Tue, Jul 21, 2020 at 9:33 PM Thomas Munro <thomas.munro@gmail.com> wrote:
>
> On Wed, Jul 22, 2020 at 3:57 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > Yeah, that is true but every time before the test the same amount of
> > data should be present in shared buffers (or OS cache) if any which
> > will help in getting consistent results. However, it is fine to
> > reboot the machine as well if that is a convenient way.
>
> We really should have an extension (pg_prewarm?) that knows how to
> kick stuff out PostgreSQL's shared buffers and the page cache
> (POSIX_FADV_DONTNEED).
>
>
+1. Clearing the OS page cache on FreeBSD is non-trivial during testing.
You can't do this on FreeBSD:
sync; echo 3 > /proc/sys/vm/drop_caches
Also, it would be nice to evict only those pages from the OS page cache
that are Postgres pages instead of having to drop everything.
Regards,
Soumyadeep (VMware)