Horton

Re: WAL Insertion Lock Improvements

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: Nathan Bossart <nathandbossart@gmail.com>, Andres Freund <andres@anarazel.de>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-05-09T03:57:21Z
Lists: pgsql-hackers 
On Tue, May 09, 2023 at 09:24:14AM +0530, Bharath Rupireddy wrote:
> I'll pick a test case that generates a reasonable amount of WAL 256
> bytes. What do you think of the following?
> 
> test-case 2: -T900, WAL ~256 bytes (for c in 1 2 4 8 16 32 64 128 256
> 512 768 1024 2048 4096 - takes 3.5hrs)
> test-case 2: -t1000000, WAL ~256 bytes
> 
> If okay, I'll fire the tests.

Sounds like a sensible duration, yes.  What's your setting for
min/max_wal_size?  I assume that there are still 16GB throttled with
target_completion at 0.9?
--
Michael

Commits

  1. Optimize pg_atomic_exchange_u32 and pg_atomic_exchange_u64.

  2. Document more assumptions of LWLock variable changes with WAL inserts

  3. Optimize WAL insertion lock acquisition and release with some atomics

  4. Avoid the use of a separate spinlock to protect a LWLock's wait queue.