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Make FP_LOCK_SLOTS_PER_BACKEND look like a function

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The FP_LOCK_SLOTS_PER_BACKEND macro looks like a constant, but it
depends on the max_locks_per_transaction GUC, and thus can change. This
is non-obvious and confusing, so make it look more like a function by
renaming it to FastPathLockSlotsPerBackend().

While at it, use the macro when initializing fast-path shared memory,
instead of using the formula.

Reported-by: Andres Freund
Discussion: https://postgr.es/m/ffiwtzc6vedo6wb4gbwelon5nefqg675t5c7an2ta7pcz646cg%40qwmkdb3l4ett
This commit is contained in:
Tomas Vondra 2025-03-04 18:33:09 +01:00
parent 91ecb5e0bc
commit c878de1db4
4 changed files with 10 additions and 9 deletions
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10
src/backend/storage/lmgr/lock.c
View File

@ -226,10 +226,10 @@ int FastPathLockGroupsPerBackend = 0;
* the FAST_PATH_SLOT macro, split it into group and index (in the group). * the FAST_PATH_SLOT macro, split it into group and index (in the group).
*/ */
#define FAST_PATH_GROUP(index) \ #define FAST_PATH_GROUP(index) \
(AssertMacro((uint32) (index) < FP_LOCK_SLOTS_PER_BACKEND), \ (AssertMacro((uint32) (index) < FastPathLockSlotsPerBackend()), \
((index) / FP_LOCK_SLOTS_PER_GROUP)) ((index) / FP_LOCK_SLOTS_PER_GROUP))
#define FAST_PATH_INDEX(index) \ #define FAST_PATH_INDEX(index) \
(AssertMacro((uint32) (index) < FP_LOCK_SLOTS_PER_BACKEND), \ (AssertMacro((uint32) (index) < FastPathLockSlotsPerBackend()), \
((index) % FP_LOCK_SLOTS_PER_GROUP)) ((index) % FP_LOCK_SLOTS_PER_GROUP))
/* Macros for manipulating proc->fpLockBits */ /* Macros for manipulating proc->fpLockBits */
@ -242,7 +242,7 @@ int FastPathLockGroupsPerBackend = 0;
#define FAST_PATH_BIT_POSITION(n, l) \ #define FAST_PATH_BIT_POSITION(n, l) \
(AssertMacro((l) >= FAST_PATH_LOCKNUMBER_OFFSET), \ (AssertMacro((l) >= FAST_PATH_LOCKNUMBER_OFFSET), \
AssertMacro((l) < FAST_PATH_BITS_PER_SLOT+FAST_PATH_LOCKNUMBER_OFFSET), \ AssertMacro((l) < FAST_PATH_BITS_PER_SLOT+FAST_PATH_LOCKNUMBER_OFFSET), \
AssertMacro((n) < FP_LOCK_SLOTS_PER_BACKEND), \ AssertMacro((n) < FastPathLockSlotsPerBackend()), \
((l) - FAST_PATH_LOCKNUMBER_OFFSET + FAST_PATH_BITS_PER_SLOT * (FAST_PATH_INDEX(n)))) ((l) - FAST_PATH_LOCKNUMBER_OFFSET + FAST_PATH_BITS_PER_SLOT * (FAST_PATH_INDEX(n))))
#define FAST_PATH_SET_LOCKMODE(proc, n, l) \ #define FAST_PATH_SET_LOCKMODE(proc, n, l) \
FAST_PATH_BITS(proc, n) |= UINT64CONST(1) << FAST_PATH_BIT_POSITION(n, l) FAST_PATH_BITS(proc, n) |= UINT64CONST(1) << FAST_PATH_BIT_POSITION(n, l)
@ -2691,7 +2691,7 @@ static bool
FastPathGrantRelationLock(Oid relid, LOCKMODE lockmode) FastPathGrantRelationLock(Oid relid, LOCKMODE lockmode)
{ {
uint32 i; uint32 i;
uint32 unused_slot = FP_LOCK_SLOTS_PER_BACKEND; uint32 unused_slot = FastPathLockSlotsPerBackend();
/* fast-path group the lock belongs to */ /* fast-path group the lock belongs to */
uint32 group = FAST_PATH_REL_GROUP(relid); uint32 group = FAST_PATH_REL_GROUP(relid);
@ -2713,7 +2713,7 @@ FastPathGrantRelationLock(Oid relid, LOCKMODE lockmode)
} }
/* If no existing entry, use any empty slot. */ /* If no existing entry, use any empty slot. */
if (unused_slot < FP_LOCK_SLOTS_PER_BACKEND) if (unused_slot < FastPathLockSlotsPerBackend())
{ {
MyProc->fpRelId[unused_slot] = relid; MyProc->fpRelId[unused_slot] = relid;
FAST_PATH_SET_LOCKMODE(MyProc, unused_slot, lockmode); FAST_PATH_SET_LOCKMODE(MyProc, unused_slot, lockmode);

4
src/backend/storage/lmgr/proc.c
View File

@ -116,7 +116,7 @@ ProcGlobalShmemSize(void)
* nicely aligned in each backend. * nicely aligned in each backend.
*/ */
fpLockBitsSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(uint64)); fpLockBitsSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(uint64));
fpRelIdSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(Oid) * FP_LOCK_SLOTS_PER_GROUP); fpRelIdSize = MAXALIGN(FastPathLockSlotsPerBackend() * sizeof(Oid));
size = add_size(size, mul_size(TotalProcs, (fpLockBitsSize + fpRelIdSize))); size = add_size(size, mul_size(TotalProcs, (fpLockBitsSize + fpRelIdSize)));
@ -231,7 +231,7 @@ InitProcGlobal(void)
* shared memory and then divide that between backends. * shared memory and then divide that between backends.
*/ */
fpLockBitsSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(uint64)); fpLockBitsSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(uint64));
fpRelIdSize = MAXALIGN(FastPathLockGroupsPerBackend * sizeof(Oid) * FP_LOCK_SLOTS_PER_GROUP); fpRelIdSize = MAXALIGN(FastPathLockSlotsPerBackend() * sizeof(Oid));
fpPtr = ShmemAlloc(TotalProcs * (fpLockBitsSize + fpRelIdSize)); fpPtr = ShmemAlloc(TotalProcs * (fpLockBitsSize + fpRelIdSize));
MemSet(fpPtr, 0, TotalProcs * (fpLockBitsSize + fpRelIdSize)); MemSet(fpPtr, 0, TotalProcs * (fpLockBitsSize + fpRelIdSize));

2
src/backend/utils/init/postinit.c
View File

@ -587,7 +587,7 @@ InitializeFastPathLocks(void)
while (FastPathLockGroupsPerBackend < FP_LOCK_GROUPS_PER_BACKEND_MAX) while (FastPathLockGroupsPerBackend < FP_LOCK_GROUPS_PER_BACKEND_MAX)
{ {
/* stop once we exceed max_locks_per_xact */ /* stop once we exceed max_locks_per_xact */
if (FastPathLockGroupsPerBackend * FP_LOCK_SLOTS_PER_GROUP >= max_locks_per_xact) if (FastPathLockSlotsPerBackend() >= max_locks_per_xact)
break; break;
FastPathLockGroupsPerBackend *= 2; FastPathLockGroupsPerBackend *= 2;

3
src/include/storage/proc.h
View File

@ -88,7 +88,8 @@ extern PGDLLIMPORT int FastPathLockGroupsPerBackend;
#define FP_LOCK_GROUPS_PER_BACKEND_MAX 1024 #define FP_LOCK_GROUPS_PER_BACKEND_MAX 1024
#define FP_LOCK_SLOTS_PER_GROUP 16 /* don't change */ #define FP_LOCK_SLOTS_PER_GROUP 16 /* don't change */
#define FP_LOCK_SLOTS_PER_BACKEND (FP_LOCK_SLOTS_PER_GROUP * FastPathLockGroupsPerBackend) #define FastPathLockSlotsPerBackend() \
(FP_LOCK_SLOTS_PER_GROUP * FastPathLockGroupsPerBackend)
/* /*
* Flags for PGPROC.delayChkptFlags * Flags for PGPROC.delayChkptFlags