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Convert ParallelBitmapHeapState->state to an atomic variable.

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Currently, this variable is a SharedBitmapState protected by a
spinlock.  By converting it to an atomic variable, we can remove the
spinlock.

Reviewed-by: Zsolt Parragi <zsolt.parragi@percona.com>
Tested-by: solai v <solai.cdac@gmail.com>
Discussion: https://postgr.es/m/alAJeRRzehDjLaF1%40nathan
This commit is contained in:
Nathan Bossart
2026-09-22 12:44:32 -05:00
parent e8a3ee5b19
commit b1ec662ec1
1 changed files with 7 additions and 16 deletions
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23
src/backend/executor/nodeBitmapHeapscan.c
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@@ -79,7 +79,6 @@ typedef enum
/* ----------------
* ParallelBitmapHeapState information
* tbmiterator iterator for scanning current pages
* mutex mutual exclusion for state
* state current state of the TIDBitmap
* cv conditional wait variable
* ----------------
@@ -87,8 +86,7 @@ typedef enum
typedef struct ParallelBitmapHeapState
{
dsa_pointer tbmiterator;
slock_t mutex;
SharedBitmapState state;
pg_atomic_uint32 state;
ConditionVariable cv;
} ParallelBitmapHeapState;
@@ -228,9 +226,7 @@ BitmapHeapNext(BitmapHeapScanState *node)
static inline void
BitmapDoneInitializingSharedState(ParallelBitmapHeapState *pstate)
{
SpinLockAcquire(&pstate->mutex);
pstate->state = BM_FINISHED;
SpinLockRelease(&pstate->mutex);
pg_atomic_write_membarrier_u32(&pstate->state, BM_FINISHED);
ConditionVariableBroadcast(&pstate->cv);
}
@@ -476,15 +472,12 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags)
static bool
BitmapShouldInitializeSharedState(ParallelBitmapHeapState *pstate)
{
SharedBitmapState state;
uint32 state;
while (1)
{
SpinLockAcquire(&pstate->mutex);
state = pstate->state;
if (pstate->state == BM_INITIAL)
pstate->state = BM_INPROGRESS;
SpinLockRelease(&pstate->mutex);
state = BM_INITIAL;
pg_atomic_compare_exchange_u32(&pstate->state, &state, BM_INPROGRESS);
/* Exit if bitmap is done, or if we're the leader. */
if (state != BM_INPROGRESS)
@@ -538,9 +531,7 @@ ExecBitmapHeapInitializeDSM(BitmapHeapScanState *node,
pstate->tbmiterator = 0;
/* Initialize the mutex */
SpinLockInit(&pstate->mutex);
pstate->state = BM_INITIAL;
pg_atomic_init_u32(&pstate->state, BM_INITIAL);
ConditionVariableInit(&pstate->cv);
@@ -565,7 +556,7 @@ ExecBitmapHeapReInitializeDSM(BitmapHeapScanState *node,
if (dsa == NULL)
return;
pstate->state = BM_INITIAL;
pg_atomic_write_u32(&pstate->state, BM_INITIAL);
if (DsaPointerIsValid(pstate->tbmiterator))
tbm_free_shared_area(dsa, pstate->tbmiterator);