diff options
Diffstat (limited to 'src/backend/storage/lmgr/s_lock.c')
| -rw-r--r-- | src/backend/storage/lmgr/s_lock.c | 35 |
1 files changed, 17 insertions, 18 deletions
diff --git a/src/backend/storage/lmgr/s_lock.c b/src/backend/storage/lmgr/s_lock.c index f1c92d70dac..3330c48a877 100644 --- a/src/backend/storage/lmgr/s_lock.c +++ b/src/backend/storage/lmgr/s_lock.c @@ -9,7 +9,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/storage/lmgr/s_lock.c,v 1.40 2005/10/15 02:49:26 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/storage/lmgr/s_lock.c,v 1.40.2.1 2005/11/22 18:23:19 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -58,27 +58,27 @@ s_lock(volatile slock_t *lock, const char *file, int line) * longer than to call the kernel, so we try to adapt the spin loop count * depending on whether we seem to be in a uniprocessor or multiprocessor. * - * Note: you might think MIN_SPINS_PER_DELAY should be just 1, but you'd be - * wrong; there are platforms where that can result in a "stuck spinlock" - * failure. This has been seen particularly on Alphas; it seems that the - * first TAS after returning from kernel space will always fail on that - * hardware. + * Note: you might think MIN_SPINS_PER_DELAY should be just 1, but you'd + * be wrong; there are platforms where that can result in a "stuck + * spinlock" failure. This has been seen particularly on Alphas; it seems + * that the first TAS after returning from kernel space will always fail + * on that hardware. * - * Once we do decide to block, we use randomly increasing pg_usleep() delays. - * The first delay is 1 msec, then the delay randomly increases to about - * one second, after which we reset to 1 msec and start again. The idea - * here is that in the presence of heavy contention we need to increase - * the delay, else the spinlock holder may never get to run and release - * the lock. (Consider situation where spinlock holder has been nice'd - * down in priority by the scheduler --- it will not get scheduled until - * all would-be acquirers are sleeping, so if we always use a 1-msec + * Once we do decide to block, we use randomly increasing pg_usleep() + * delays. The first delay is 1 msec, then the delay randomly increases to + * about one second, after which we reset to 1 msec and start again. The + * idea here is that in the presence of heavy contention we need to + * increase the delay, else the spinlock holder may never get to run and + * release the lock. (Consider situation where spinlock holder has been + * nice'd down in priority by the scheduler --- it will not get scheduled + * until all would-be acquirers are sleeping, so if we always use a 1-msec * sleep, there is a real possibility of starvation.) But we can't just * clamp the delay to an upper bound, else it would take a long time to * make a reasonable number of tries. * - * We time out and declare error after NUM_DELAYS delays (thus, exactly that - * many tries). With the given settings, this will usually take 2 or so - * minutes. It seems better to fix the total number of tries (and thus + * We time out and declare error after NUM_DELAYS delays (thus, exactly + * that many tries). With the given settings, this will usually take 2 or + * so minutes. It seems better to fix the total number of tries (and thus * the probability of unintended failure) than to fix the total time * spent. * @@ -251,7 +251,6 @@ _success: \n\ ); } #endif /* __m68k__ && !__linux__ */ - #else /* not __GNUC__ */ /* |