Horton

Re: SLRU optimization - configurable buffer pool and partitioning the SLRU lock

Alexander Law <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>, "Andrey M. Borodin" <x4mmm@yandex-team.ru>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, tender wang <tndrwang@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Tomas Vondra <tomas.vondra@enterprisedb.com>
Date: 2024-04-03T12:00:00Z
Lists: pgsql-hackers 
Hello Alvaro,

27.02.2024 20:33, Alvaro Herrera wrote:
> Here's the complete set, with these two names using the singular.
>

I've managed to trigger an assert added by 53c2a97a9.
Please try the following script against a server compiled with
-DTEST_SUMMARIZE_SERIAL (initially I observed this failure without the
define, it just simplifies reproducing...):
# initdb & start ...

createdb test
echo "
SELECT pg_current_xact_id() AS tx
\gset

SELECT format('CREATE TABLE t%s(i int)', g)
   FROM generate_series(1, 1022 - :tx) g
\gexec

BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
SELECT pg_current_xact_id();
SELECT pg_sleep(5);
" | psql test &

echo "
SELECT pg_sleep(1);
BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
SELECT 1 INTO a;
COMMIT;

BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
SELECT 2 INTO b;
" | psql test

It fails for me with the following stack trace:
TRAP: failed Assert("LWLockHeldByMeInMode(SimpleLruGetBankLock(ctl, pageno), LW_EXCLUSIVE)"), File: "slru.c", Line: 366, 
PID: 21711
ExceptionalCondition at assert.c:52:13
SimpleLruZeroPage at slru.c:369:11
SerialAdd at predicate.c:921:20
SummarizeOldestCommittedSxact at predicate.c:1521:2
GetSerializableTransactionSnapshotInt at predicate.c:1787:16
GetSerializableTransactionSnapshot at predicate.c:1691:1
GetTransactionSnapshot at snapmgr.c:264:21
exec_simple_query at postgres.c:1162:4
...

Best regards,
Alexander

Commits

  1. Fix zeroing of pg_serial page without SLRU bank lock

  2. Fix misspelled assertions

  3. GUC table: Add description to computed variables

  4. Improve performance of subsystems on top of SLRU

  5. Rename SLRU elements in view pg_stat_slru

  6. Use atomic access for SlruShared->latest_page_number

  7. Split use of SerialSLRULock, creating SerialControlLock

  8. Index SLRUs by 64-bit integers rather than by 32-bit integers

  9. Add a macro templatized hashtable.