Thread: pgsql: TODO item not needed anymore now that the buffer cache is
pgsql: TODO item not needed anymore now that the buffer cache is
From
momjian@postgresql.org (Bruce Momjian)
Date:
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.
Modified Files:
--------------
pgsql/doc:
TODO (r1.2197 -> r1.2198)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/TODO.diff?r1=1.2197&r2=1.2198)
pgsql/doc/src/FAQ:
TODO.html (r1.698 -> r1.699)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/FAQ/TODO.html.diff?r1=1.698&r2=1.699)
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. Kris Jurka
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. +