Horton

Re: Replace known_assigned_xids_lck by memory barrier

Michail Nikolaev <michail.nikolaev@gmail.com>

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From: Michail Nikolaev <michail.nikolaev@gmail.com>
To: Nathan Bossart <nathandbossart@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2023-08-16T19:29:10Z
Lists: pgsql-hackers 
Hello, good question!

Thanks for your edits.

As answer: probably we need to change
"If we know that we're holding ProcArrayLock exclusively, we don't
need the read barrier."
to
"If we're removing xid, we don't need the read barrier because only
the startup process can remove and add xids to KnownAssignedXids"

Best regards,
Mikhail.

Commits

  1. Replace known_assigned_xids_lck with memory barriers.

  2. Replace the KnownAssignedXids hash table with a sorted-array data structure,