Re: Bug: Buffer cache is not scan resistant

"Simon Riggs" <simon@2ndquadrant.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