diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/include/storage/lwlock.h | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/src/include/storage/lwlock.h b/src/include/storage/lwlock.h index 133ed6dc834..8bd93c3b819 100644 --- a/src/include/storage/lwlock.h +++ b/src/include/storage/lwlock.h @@ -58,16 +58,17 @@ typedef struct LWLock * LWLockPadded can be used for cases where we want each lock to be an entire * cache line. * - * On 32-bit platforms, an LWLockMinimallyPadded might actually contain more - * than the absolute minimum amount of padding required to keep a lock from - * crossing a cache line boundary, because an unpadded LWLock might fit into - * 16 bytes. We ignore that possibility when determining the minimal amount - * of padding. Older releases had larger LWLocks, so 32 really was the - * minimum, and packing them in tighter might hurt performance. + * An LWLockMinimallyPadded might contain more than the absolute minimum amount + * of padding required to keep a lock from crossing a cache line boundary, + * because an unpadded LWLock will normally fit into 16 bytes. We ignore that + * possibility when determining the minimal amount of padding. Older releases + * had larger LWLocks, so 32 really was the minimum, and packing them in + * tighter might hurt performance. * * LWLOCK_MINIMAL_SIZE should be 32 on basically all common platforms, but - * because slock_t is more than 2 bytes on some obscure platforms, we allow - * for the possibility that it might be 64. + * because pg_atomic_uint32 is more than 4 bytes on some obscure platforms, we + * allow for the possibility that it might be 64. Even on those platforms, + * we probably won't exceed 32 bytes unless LOCK_DEBUG is defined. */ #define LWLOCK_PADDED_SIZE PG_CACHE_LINE_SIZE #define LWLOCK_MINIMAL_SIZE (sizeof(LWLock) <= 32 ? 32 : 64) |