Re: Spurious "apparent wraparound" via SimpleLruTruncate() rounding

x4mmm@yandex-team.ru

From: Andrey Borodin <x4mmm@yandex-team.ru>

To: Noah Misch <noah@leadboat.com>

Cc: Tom Lane <tgl@sss.pgh.pa.us>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, pgsql-hackers@postgresql.org

Date: 2021-01-10T06:44:14Z

Lists: pgsql-hackers


> 10 янв. 2021 г., в 03:15, Noah Misch <noah@leadboat.com> написал(а):
> 
> No; it deletes the most recent ~1B and leaves the older segments.  An
> exception is multixact, as described in the commit message and the patch's
> change to a comment in TruncateMultiXact().

Thanks for clarification.
One more thing: retention point at 3/4 of overall space (half of wraparound) seems more or less random to me. Why not 5/8 or 9/16?

Can you please send revised patches with fixes?

Thanks!

Best regards, Andrey Borodin.

Commits

Prevent excess SimpleLruTruncate() deletion.
- c424c75f5382 9.5.25 landed
- 9afba9b0e282 10.16 landed
- 677f6cb1d987 11.11 landed
- 66087f7e922c 12.6 landed
- 1a31d8c52db4 9.6.21 landed
- 6eb3fc7fcd89 13.2 landed
- 6db992833c04 14.0 landed
Fix unlinking of SLRU segments.
- c732c3f8c122 14.0 cited
Defer flushing of SLRU files.
- dee663f78439 14.0 cited
Change XID and mxact limits to warn at 40M and stop at 3M.
- cd5e82256de5 14.0 cited