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Revert recent change to RequestNamedLWLockTranche().

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Commit 38b602b028 modified this function to allocate enough space
for MAX_NAMED_TRANCHES (256) requests, which is likely far more
than most clusters need.  This commit reverts that change so that
it first allocates enough space for only 16 requests and resizes
the array when necessary.  While at it, remove the check for too
many tranches from this function.  We can now rely on
InitializeLWLocks() to do that check via its calls to
LWLockNewTrancheId() for the named tranches.

Reviewed-by: Sami Imseih <samimseih@gmail.com>
Discussion: https://postgr.es/m/aLmzwC2dRbqk14y6%40nathan
This commit is contained in:
Nathan Bossart 2025-09-04 15:34:48 -05:00
parent f0478149c3
commit d814d7fc3d
1 changed files with 12 additions and 6 deletions
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18
src/backend/storage/lmgr/lwlock.c
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@ -610,6 +610,7 @@ void
RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks) RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)
{ {
NamedLWLockTrancheRequest *request; NamedLWLockTrancheRequest *request;
static int NamedLWLockTrancheRequestsAllocated;
if (!process_shmem_requests_in_progress) if (!process_shmem_requests_in_progress)
elog(FATAL, "cannot request additional LWLocks outside shmem_request_hook"); elog(FATAL, "cannot request additional LWLocks outside shmem_request_hook");
@ -628,17 +629,22 @@ RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)
if (NamedLWLockTrancheRequestArray == NULL) if (NamedLWLockTrancheRequestArray == NULL)
{ {
NamedLWLockTrancheRequestsAllocated = 16;
NamedLWLockTrancheRequestArray = (NamedLWLockTrancheRequest *) NamedLWLockTrancheRequestArray = (NamedLWLockTrancheRequest *)
MemoryContextAlloc(TopMemoryContext, MemoryContextAlloc(TopMemoryContext,
MAX_NAMED_TRANCHES NamedLWLockTrancheRequestsAllocated
* sizeof(NamedLWLockTrancheRequest)); * sizeof(NamedLWLockTrancheRequest));
} }
if (NamedLWLockTrancheRequests >= MAX_NAMED_TRANCHES) if (NamedLWLockTrancheRequests >= NamedLWLockTrancheRequestsAllocated)
ereport(ERROR, {
(errmsg("maximum number of tranches already registered"), int i = pg_nextpower2_32(NamedLWLockTrancheRequests + 1);
errdetail("No more than %d tranches may be registered.",
MAX_NAMED_TRANCHES))); NamedLWLockTrancheRequestArray = (NamedLWLockTrancheRequest *)
repalloc(NamedLWLockTrancheRequestArray,
i * sizeof(NamedLWLockTrancheRequest));
NamedLWLockTrancheRequestsAllocated = i;
}
request = &NamedLWLockTrancheRequestArray[NamedLWLockTrancheRequests]; request = &NamedLWLockTrancheRequestArray[NamedLWLockTrancheRequests];
strlcpy(request->tranche_name, tranche_name, NAMEDATALEN); strlcpy(request->tranche_name, tranche_name, NAMEDATALEN);