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Added custom mutex spin.

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A fixed max spin count is used -- with benchmark results showing it
solves almost all problems. As the benchmark used was rather intense,
the upper bound could be a little bit high. However it should offer a
good tradeoff between spinning and blocking.
This commit is contained in:
Qi Wang 2017-03-15 15:31:37 -07:00 committed by Qi Wang
parent 20b8c70e9f
commit 74f78cafda
3 changed files with 27 additions and 17 deletions
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12
include/jemalloc/internal/mutex_inlines.h
View File

@ -52,11 +52,13 @@ malloc_mutex_lock(tsdn_t *tsdn, malloc_mutex_t *mutex) {
malloc_mutex_lock_slow(mutex);
}
/* We own the lock now. Update a few counters. */
mutex_prof_data_t *data = &mutex->prof_data;
data->n_lock_ops++;
if (data->prev_owner != tsdn) {
data->prev_owner = tsdn;
data->n_owner_switches++;
if (config_stats) {
mutex_prof_data_t *data = &mutex->prof_data;
data->n_lock_ops++;
if (data->prev_owner != tsdn) {
data->prev_owner = tsdn;
data->n_owner_switches++;
}
}
}
witness_lock(tsdn, &mutex->witness);

16
include/jemalloc/internal/mutex_types.h
View File

@ -4,6 +4,12 @@
typedef struct mutex_prof_data_s mutex_prof_data_t;
typedef struct malloc_mutex_s malloc_mutex_t;
/*
* Based on benchmark results, a fixed spin with this amount of retries works
* well for our critical sections.
*/
#define MALLOC_MUTEX_MAX_SPIN 250
#ifdef _WIN32
# if _WIN32_WINNT >= 0x0600
# define MALLOC_MUTEX_LOCK(m) AcquireSRWLockExclusive(&(m)->lock)
@ -45,20 +51,10 @@ typedef struct malloc_mutex_s malloc_mutex_t;
{{{LOCK_PROF_DATA_INITIALIZER, PTHREAD_MUTEX_INITIALIZER, NULL}}, \
WITNESS_INITIALIZER("mutex", WITNESS_RANK_OMIT)}
#else
/* TODO: get rid of adaptive mutex once we do our own spin. */
# if (defined(JEMALLOC_HAVE_PTHREAD_MUTEX_ADAPTIVE_NP) && \
defined(PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP))
# define MALLOC_MUTEX_TYPE PTHREAD_MUTEX_ADAPTIVE_NP
# define MALLOC_MUTEX_INITIALIZER \
{{{LOCK_PROF_DATA_INITIALIZER, \
PTHREAD_ADAPTIVE_MUTEX_INITIALIZER_NP}}, \
WITNESS_INITIALIZER("mutex", WITNESS_RANK_OMIT)}
# else
# define MALLOC_MUTEX_TYPE PTHREAD_MUTEX_DEFAULT
# define MALLOC_MUTEX_INITIALIZER \
{{{LOCK_PROF_DATA_INITIALIZER, PTHREAD_MUTEX_INITIALIZER}}, \
WITNESS_INITIALIZER("mutex", WITNESS_RANK_OMIT)}
# endif
#endif
#endif /* JEMALLOC_INTERNAL_MUTEX_TYPES_H */

16
src/mutex.c
View File

@ -69,14 +69,26 @@ void
malloc_mutex_lock_slow(malloc_mutex_t *mutex) {
mutex_prof_data_t *data = &mutex->prof_data;
{//TODO: a smart spin policy
if (ncpus == 1) {
goto label_spin_done;
}
int cnt = 0, max_cnt = MALLOC_MUTEX_MAX_SPIN;
do {
CPU_SPINWAIT;
if (!malloc_mutex_trylock(mutex)) {
data->n_spin_acquired++;
return;
}
}
} while (cnt++ < max_cnt);
if (!config_stats) {
/* Only spin is useful when stats is off. */
malloc_mutex_lock_final(mutex);
return;
}
nstime_t now, before;
label_spin_done:
nstime_init(&now, 0);
nstime_update(&now);
nstime_copy(&before, &now);