Add an option to have 64-byte (cache line) aligned mutexes.

lib/isc/pthreads/condition.c

@@ -53,7 +53,7 @@ isc_condition_waituntil(isc_condition_t *c, isc_mutex_t *m, isc_time_t *t) {
 	ts.tv_nsec = (long)isc_time_nanoseconds(t);
 
 	do {
-#if ISC_MUTEX_PROFILE
+#if ISC_MUTEX_STRUCT
 		presult = pthread_cond_timedwait(c, &m->mutex, &ts);
 #else
 		presult = pthread_cond_timedwait(c, m, &ts);

lib/isc/pthreads/include/isc/condition.h

@@ -26,7 +26,7 @@ typedef pthread_cond_t isc_condition_t;
 	((pthread_cond_init((cp), NULL) == 0) ? \
 	 ISC_R_SUCCESS : ISC_R_UNEXPECTED)
 
-#if ISC_MUTEX_PROFILE
+#if ISC_MUTEX_STRUCT
 #define isc_condition_wait(cp, mp) \
 	((pthread_cond_wait((cp), &((mp)->mutex)) == 0) ? \
 	 ISC_R_SUCCESS : ISC_R_UNEXPECTED)

lib/isc/pthreads/include/isc/mutex.h

@@ -37,6 +37,15 @@ extern pthread_mutexattr_t isc__mutex_attrs;
 
 /* XXX We could do fancier error handling... */
 
+/*!
+ * Define ISC_MUTEX_STRUCT to turn on padding of isc_mutex_t to cache
+ * line size, so that no two mutexes are ever in the same cache line.
+ * We assume that cache line is 64bytes here.
+ */
+#ifndef ISC_MUTEX_STRUCT
+#define ISC_MUTEX_STRUCT 1
+#endif
+#define ISC_MUTEX_STRUCT_PAD (64-sizeof(pthread_mutex_t)-sizeof(void*))
 /*!
  * Define ISC_MUTEX_PROFILE to turn on profiling of mutexes by line.  When
  * enabled, isc_mutex_stats() can be used to print a table showing the
@@ -48,11 +57,16 @@ extern pthread_mutexattr_t isc__mutex_attrs;
 #endif
 
 #if ISC_MUTEX_PROFILE
+#define ISC_MUTEX_STRUCT 1
+#endif
+
+#if ISC_MUTEX_STRUCT
 typedef struct isc_mutexstats isc_mutexstats_t;
 
 typedef struct {
 	pthread_mutex_t		mutex;	/*%< The actual mutex. */
 	isc_mutexstats_t *	stats;	/*%< Mutex statistics. */
+	char pad[ISC_MUTEX_STRUCT_PAD];
 } isc_mutex_t;
 #else
 typedef pthread_mutex_t	isc_mutex_t;
@@ -76,6 +90,10 @@ isc_result_t isc__mutex_init(isc_mutex_t *mp, const char *file, unsigned int lin
 #if ISC_MUTEX_PROFILE
 #define isc_mutex_lock(mp) \
 	isc_mutex_lock_profile((mp), __FILE__, __LINE__)
+#elif ISC_MUTEX_STRUCT
+#define isc_mutex_lock(mp) \
+	((pthread_mutex_lock(&(mp)->mutex) == 0) ? \
+	 ISC_R_SUCCESS : ISC_R_UNEXPECTED)
 #else
 #define isc_mutex_lock(mp) \
 	((pthread_mutex_lock((mp)) == 0) ? \
@@ -85,13 +103,17 @@ isc_result_t isc__mutex_init(isc_mutex_t *mp, const char *file, unsigned int lin
 #if ISC_MUTEX_PROFILE
 #define isc_mutex_unlock(mp) \
 	isc_mutex_unlock_profile((mp), __FILE__, __LINE__)
+#elif ISC_MUTEX_STRUCT
+#define isc_mutex_unlock(mp) \
+	((pthread_mutex_unlock(&(mp)->mutex) == 0) ? \
+	 ISC_R_SUCCESS : ISC_R_UNEXPECTED)
 #else
 #define isc_mutex_unlock(mp) \
 	((pthread_mutex_unlock((mp)) == 0) ? \
 	 ISC_R_SUCCESS : ISC_R_UNEXPECTED)
 #endif
 
-#if ISC_MUTEX_PROFILE
+#if ISC_MUTEX_STRUCT
 #define isc_mutex_trylock(mp) \
 	((pthread_mutex_trylock((&(mp)->mutex)) == 0) ? \
 	 ISC_R_SUCCESS : ISC_R_LOCKBUSY)
@@ -101,7 +123,7 @@ isc_result_t isc__mutex_init(isc_mutex_t *mp, const char *file, unsigned int lin
 	 ISC_R_SUCCESS : ISC_R_LOCKBUSY)
 #endif
 
-#if ISC_MUTEX_PROFILE
+#if ISC_MUTEX_STRUCT
 #define isc_mutex_destroy(mp) \
 	((pthread_mutex_destroy((&(mp)->mutex)) == 0) ? \
 	 ISC_R_SUCCESS : ISC_R_UNEXPECTED)

lib/isc/pthreads/mutex.c

@@ -284,10 +284,17 @@ isc__mutex_init(isc_mutex_t *mp, const char *file, unsigned int line) {
 #ifdef HAVE_PTHREAD_MUTEX_ADAPTIVE_NP
 	result = isc_once_do(&once_attr, initialize_attr);
 	RUNTIME_CHECK(result == ISC_R_SUCCESS);
-
+#ifdef ISC_MUTEX_STRUCT
+	err = pthread_mutex_init(&mp->mutex, &attr);
+#else
 	err = pthread_mutex_init(mp, &attr);
+#endif
 #else /* HAVE_PTHREAD_MUTEX_ADAPTIVE_NP */
+#ifdef ISC_MUTEX_STRUCT
+	err = pthread_mutex_init(&mp->mutex, ISC__MUTEX_ATTRS);
+#else
 	err = pthread_mutex_init(mp, ISC__MUTEX_ATTRS);
+#endif
 #endif /* HAVE_PTHREAD_MUTEX_ADAPTIVE_NP */
 
 	if (err == ENOMEM)