postgres.git / summary / log / commit / refs

commit    d814d7fc3d5257ae258b502229fc7ca97c97270a
Author:   Nathan Bossart <nathan@postgresql.org>
Date:     Thu Sep 04 20:34:48 2025 +0000

    Revert recent change to RequestNamedLWLockTranche().
    
    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


 src/backend/storage/lmgr/lwlock.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/backend/storage/lmgr/lwlock.c b/src/backend/storage/lmgr/lwlock.c
index 258cdebd0f5..fcbac5213a5 100644
--- a/src/backend/storage/lmgr/lwlock.c
+++ b/src/backend/storage/lmgr/lwlock.c
@@ -610,6 +610,7 @@ void
 RequestNamedLWLockTranche(const char *tranche_name, int num_lwlocks)
 {
 	NamedLWLockTrancheRequest *request;
+	static int	NamedLWLockTrancheRequestsAllocated;
 
 	if (!process_shmem_requests_in_progress)
 		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)
 	{
+		NamedLWLockTrancheRequestsAllocated = 16;
 		NamedLWLockTrancheRequestArray = (NamedLWLockTrancheRequest *)
 			MemoryContextAlloc(TopMemoryContext,
-							   MAX_NAMED_TRANCHES
+							   NamedLWLockTrancheRequestsAllocated
 							   * sizeof(NamedLWLockTrancheRequest));
 	}
 
-	if (NamedLWLockTrancheRequests >= MAX_NAMED_TRANCHES)
-		ereport(ERROR,
-				(errmsg("maximum number of tranches already registered"),
-				 errdetail("No more than %d tranches may be registered.",
-						   MAX_NAMED_TRANCHES)));
+	if (NamedLWLockTrancheRequests >= NamedLWLockTrancheRequestsAllocated)
+	{
+		int			i = pg_nextpower2_32(NamedLWLockTrancheRequests + 1);
+
+		NamedLWLockTrancheRequestArray = (NamedLWLockTrancheRequest *)
+			repalloc(NamedLWLockTrancheRequestArray,
+					 i * sizeof(NamedLWLockTrancheRequest));
+		NamedLWLockTrancheRequestsAllocated = i;
+	}
 
 	request = &NamedLWLockTrancheRequestArray[NamedLWLockTrancheRequests];
 	strlcpy(request->tranche_name, tranche_name, NAMEDATALEN);


[parent: f0478149c34d]