Re: pgsql: TODO item not needed anymore now that the buffer cache is

Kris Jurka wrote:
>
>
> On Fri, 1 Jun 2007, Bruce Momjian wrote:
>
> > Log Message:
> > -----------
> > TODO item not needed anymore now that the buffer cache is
> > scan-resistant:
> >
> > <
> > < * Allow free-behind capability for large sequential scans, perhaps using
> > <   posix_fadvise()
> > <
> > <   Posix_fadvise() can control both sequential/random file caching and
> > <   free-behind behavior, but it is unclear how the setting affects other
> > <   backends that also have the file open, and the feature is not supported
> > <   on all operating systems.
> >
>
> This todo item is about telling the OS cache that we don't want these
> buffers kept around, not about pg's own buffer cache.  So I think it's
> still valid.

Agreed, re-added, and clarified it is for the kernel cache:

* Allow free-behind capability for large sequential scans to avoid
  kernel cache spoiling

  Posix_fadvise() can control both sequential/random file caching and
  free-behind behavior, but it is unclear how the setting affects other
  backends that also have the file open, and the feature is not supported
  on all operating systems.

--
  Bruce Momjian  <bruce@momjian.us>          http://momjian.us
  EnterpriseDB                               http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +