Re: [PATCHES] scan_recycle_buffers

On Sat, 2007-03-10 at 23:26 +1300, Mark Kirkwood wrote:
> Simon Riggs wrote:
> > New patch enclosed, implementation as you've requested.
> >
> > Not ready to apply yet, but good for testing.
> >
>
> A quick test using the setup for "Buffer cache is not scan resistant"
> thread:
>
> Firstly vanilla 8.3 from 20070310:
>
> Shared Buffers Elapsed vmstat IO rate
> -------------- ------- --------------
> 400MB 101 s 122 MB/s
> 128KB 79 s 155 MB/s [1]
>
> Now apply cycle scan v2:
>
> Shared Buffers Scan_recycle_buffers Elapsed vmstat IO rate
> -------------- -------------------- ------- -------------
> 400MB 0 101 s 122 MB/s
> 400MB 8 78 s 155 MB/s
> 400MB 16 77 s 155 MB/s
> 400MB 32 78 s 155 MB/s
> 400MB 64 82 s 148 MB/s
> 400MB 128 93 s 128 MB/s
>
> Certainly seems to have the desired effect!
>
> Cheers
>
> Mark
>
> [1] I'm not seeing 166 MB/s like previous 8.2.3 data, however 8.3 PGDATA
> is located further toward the end of the disk array - which I suspect is
> limiting the IO rate a little.

That's good news, thanks very much for testing that.

Before we can claim success, we need a few more tests on VACUUM, COPY
and a null test case to show it doesn't effect typical workloads, except
to improve vacuuming. I'll see if we can arrange those at EDB on a
reasonable size system.

--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com