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Use atomic access for SlruShared->latest_page_number

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The new concurrency model proposed for slru.c to improve performance
does not include any single lock that would coordinate processes
doing concurrent reads/writes on SlruShared->latest_page_number.
We can instead use atomic reads and writes for that variable.

Author: Dilip Kumar <dilipbalaut@gmail.com>
Reviewed-by: Andrey M. Borodin <x4mmm@yandex-team.ru>
Discussion: https://postgr.es/m/CAFiTN-vzDvNz=ExGXz6gdyjtzGixKSqs0mKHMmaQ8sOSEFZ33A@mail.gmail.com
This commit is contained in:
Alvaro Herrera
2024-02-06 10:54:10 +01:00
parent b83033c3cf
commit d172b717c6
5 changed files with 53 additions and 32 deletions
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28
src/backend/access/transam/multixact.c
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@@ -2017,13 +2017,15 @@ StartupMultiXact(void)
* Initialize offset's idea of the latest page number.
*/
pageno = MultiXactIdToOffsetPage(multi);
MultiXactOffsetCtl->shared->latest_page_number = pageno;
pg_atomic_write_u64(&MultiXactOffsetCtl->shared->latest_page_number,
pageno);
/*
* Initialize member's idea of the latest page number.
*/
pageno = MXOffsetToMemberPage(offset);
MultiXactMemberCtl->shared->latest_page_number = pageno;
pg_atomic_write_u64(&MultiXactMemberCtl->shared->latest_page_number,
pageno);
}
/*
@@ -2047,14 +2049,15 @@ TrimMultiXact(void)
oldestMXactDB = MultiXactState->oldestMultiXactDB;
LWLockRelease(MultiXactGenLock);
/* Clean up offsets state */
LWLockAcquire(MultiXactOffsetSLRULock, LW_EXCLUSIVE);
/*
* (Re-)Initialize our idea of the latest page number for offsets.
*/
pageno = MultiXactIdToOffsetPage(nextMXact);
MultiXactOffsetCtl->shared->latest_page_number = pageno;
pg_atomic_write_u64(&MultiXactOffsetCtl->shared->latest_page_number,
pageno);
/* Clean up offsets state */
LWLockAcquire(MultiXactOffsetSLRULock, LW_EXCLUSIVE);
/*
* Zero out the remainder of the current offsets page. See notes in
@@ -2081,14 +2084,16 @@ TrimMultiXact(void)
LWLockRelease(MultiXactOffsetSLRULock);
/* And the same for members */
LWLockAcquire(MultiXactMemberSLRULock, LW_EXCLUSIVE);
/*
* And the same for members.
*
* (Re-)Initialize our idea of the latest page number for members.
*/
pageno = MXOffsetToMemberPage(offset);
MultiXactMemberCtl->shared->latest_page_number = pageno;
pg_atomic_write_u64(&MultiXactMemberCtl->shared->latest_page_number,
pageno);
LWLockAcquire(MultiXactMemberSLRULock, LW_EXCLUSIVE);
/*
* Zero out the remainder of the current members page. See notes in
@@ -3333,7 +3338,8 @@ multixact_redo(XLogReaderState *record)
* SimpleLruTruncate.
*/
pageno = MultiXactIdToOffsetPage(xlrec.endTruncOff);
MultiXactOffsetCtl->shared->latest_page_number = pageno;
pg_atomic_write_u64(&MultiXactOffsetCtl->shared->latest_page_number,
pageno);
PerformOffsetsTruncation(xlrec.startTruncOff, xlrec.endTruncOff);
LWLockRelease(MultiXactTruncationLock);