diff options
Diffstat (limited to 'src/backend/storage/buffer/bufmgr.c')
| -rw-r--r-- | src/backend/storage/buffer/bufmgr.c | 36 |
1 files changed, 27 insertions, 9 deletions
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c index a768fb129ae..eb55102b0d7 100644 --- a/src/backend/storage/buffer/bufmgr.c +++ b/src/backend/storage/buffer/bufmgr.c @@ -6358,23 +6358,41 @@ rlocator_comparator(const void *p1, const void *p2) uint32 LockBufHdr(BufferDesc *desc) { - SpinDelayStatus delayStatus; uint32 old_buf_state; Assert(!BufferIsLocal(BufferDescriptorGetBuffer(desc))); - init_local_spin_delay(&delayStatus); - while (true) { - /* set BM_LOCKED flag */ + /* + * Always try once to acquire the lock directly, without setting up + * the spin-delay infrastructure. The work necessary for that shows up + * in profiles and is rarely necessary. + */ old_buf_state = pg_atomic_fetch_or_u32(&desc->state, BM_LOCKED); - /* if it wasn't set before we're OK */ - if (!(old_buf_state & BM_LOCKED)) - break; - perform_spin_delay(&delayStatus); + if (likely(!(old_buf_state & BM_LOCKED))) + break; /* got lock */ + + /* and then spin without atomic operations until lock is released */ + { + SpinDelayStatus delayStatus; + + init_local_spin_delay(&delayStatus); + + while (old_buf_state & BM_LOCKED) + { + perform_spin_delay(&delayStatus); + old_buf_state = pg_atomic_read_u32(&desc->state); + } + finish_spin_delay(&delayStatus); + } + + /* + * Retry. The lock might obviously already be re-acquired by the time + * we're attempting to get it again. + */ } - finish_spin_delay(&delayStatus); + return old_buf_state | BM_LOCKED; } |