Re: Bug: Buffer cache is not scan resistant

"Simon Riggs" <simon(at)2ndquadrant(dot)com> wrote:

> > > With the default
> > > value of scan_recycle_buffers(=0), VACUUM seems to use all of buffers in pool,
> > > just like existing sequential scans. Is this intended?
> >
> New test version enclosed, where scan_recycle_buffers = 0 doesn't change
> existing VACUUM behaviour.

This is a result with scan_recycle_buffers.v3.patch. I used normal VACUUM
with background load using slowdown-ed pgbench in this instance. I believe
the patch is useful in normal cases, not only for VACUUM FREEZE.

N | time | WAL flush(*)
-----+--------+-----------
0 | 112.8s | 44.3%
1 | 148.9s | 52.1%
8 | 105.1s | 17.6%
16 | 96.9s | 8.7%
32 | 103.9s | 6.3%
64 | 89.4s | 6.6%
128 | 80.0s | 3.8%

Regards,
---
ITAGAKI Takahiro
NTT Open Source Software Center