Horton

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

x4mmm@yandex-team.ru

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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: 2021-01-12T16:41:19Z
Lists: pgsql-hackers 

> 12 янв. 2021 г., в 13:49, Noah Misch <noah@leadboat.com> написал(а):
> 
> What do you think of abandoning slru-truncate-t-insurance entirely?  As of
> https://postgr.es/m/20200330052809.GB2324620@rfd.leadboat.com I liked the idea
> behind it, despite its complicating the system for hackers and DBAs.  The
> TruncateMultiXact() interaction rendered it less appealing.  In v14+, commit
> cd5e822 mitigates the kind of bugs that slru-truncate-t-insurance mitigates,
> further reducing the latter's value.  slru-truncate-t-insurance does mitigate
> larger trespasses into unlink-eligible space, though.
I seem to me that not committing an insurance patch is not a mistake. Let's abandon slru-truncate-t-insurance for now.

>> Fix <slru-truncate-modulo-v6.patch> certainly worth backpatching.
> 
> I'll push it on Saturday, probably.
Thanks!

Best regards, Andrey Borodin.

Commits

  1. Prevent excess SimpleLruTruncate() deletion.

  2. Fix unlinking of SLRU segments.

  3. Defer flushing of SLRU files.

  4. Change XID and mxact limits to warn at 40M and stop at 3M.