diff options
Diffstat (limited to 'lib/isc/stats.c')
| -rw-r--r-- | lib/isc/stats.c | 78 |
1 files changed, 56 insertions, 22 deletions
diff --git a/lib/isc/stats.c b/lib/isc/stats.c index 03d2a8a7d103..368dadfc323e 100644 --- a/lib/isc/stats.c +++ b/lib/isc/stats.c @@ -35,13 +35,45 @@ #define ISC_STATS_MAGIC ISC_MAGIC('S', 't', 'a', 't') #define ISC_STATS_VALID(x) ISC_MAGIC_VALID(x, ISC_STATS_MAGIC) -#ifndef ISC_STATS_USEMULTIFIELDS -#if defined(ISC_RWLOCK_USEATOMIC) && defined(ISC_PLATFORM_HAVEXADD) && !defined(ISC_PLATFORM_HAVEXADDQ) +/*% + * Local macro confirming prescence of 64-bit + * increment and store operations, just to make + * the later macros simpler + */ +#if defined(ISC_PLATFORM_HAVEXADDQ) && defined(ISC_PLATFORM_HAVEATOMICSTOREQ) +#define ISC_STATS_HAVEATOMICQ 1 +#else +#define ISC_STATS_HAVEATOMICQ 0 +#endif + +/*% + * Only lock the counters if 64-bit atomic operations are + * not available but cheap atomic lock operations are. + * On a modern 64-bit system this should never be the case. + * + * Normal locks are too expensive to be used whenever a counter + * is updated. + */ +#if !ISC_STATS_HAVEATOMICQ && defined(ISC_RWLOCK_HAVEATOMIC) +#define ISC_STATS_LOCKCOUNTERS 1 +#else +#define ISC_STATS_LOCKCOUNTERS 0 +#endif + +/*% + * If 64-bit atomic operations are not available but + * 32-bit operations are then split the counter into two, + * using the atomic operations to try to ensure that any carry + * from the low word is correctly carried into the high word. + * + * Otherwise, just rely on standard 64-bit data types + * and operations + */ +#if !ISC_STATS_HAVEATOMICQ && defined(ISC_PLATFORM_HAVEXADD) #define ISC_STATS_USEMULTIFIELDS 1 #else #define ISC_STATS_USEMULTIFIELDS 0 #endif -#endif /* ISC_STATS_USEMULTIFIELDS */ #if ISC_STATS_USEMULTIFIELDS typedef struct { @@ -65,7 +97,7 @@ struct isc_stats { * Locked by counterlock or unlocked if efficient rwlock is not * available. */ -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS isc_rwlock_t counterlock; #endif isc_stat_t *counters; @@ -111,7 +143,7 @@ create_stats(isc_mem_t *mctx, int ncounters, isc_stats_t **statsp) { goto clean_counters; } -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS result = isc_rwlock_init(&stats->counterlock, 0, 0); if (result != ISC_R_SUCCESS) goto clean_copiedcounters; @@ -131,7 +163,7 @@ create_stats(isc_mem_t *mctx, int ncounters, isc_stats_t **statsp) { clean_counters: isc_mem_put(mctx, stats->counters, sizeof(isc_stat_t) * ncounters); -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS clean_copiedcounters: isc_mem_put(mctx, stats->copiedcounters, sizeof(isc_stat_t) * ncounters); @@ -177,7 +209,7 @@ isc_stats_detach(isc_stats_t **statsp) { sizeof(isc_stat_t) * stats->ncounters); UNLOCK(&stats->lock); DESTROYLOCK(&stats->lock); -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS isc_rwlock_destroy(&stats->counterlock); #endif isc_mem_putanddetach(&stats->mctx, stats, sizeof(*stats)); @@ -198,7 +230,7 @@ static inline void incrementcounter(isc_stats_t *stats, int counter) { isc_int32_t prev; -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS /* * We use a "read" lock to prevent other threads from reading the * counter while we "writing" a counter field. The write access itself @@ -219,7 +251,7 @@ incrementcounter(isc_stats_t *stats, int counter) { */ if (prev == (isc_int32_t)0xffffffff) isc_atomic_xadd((isc_int32_t *)&stats->counters[counter].hi, 1); -#elif defined(ISC_PLATFORM_HAVEXADDQ) +#elif ISC_STATS_HAVEATOMICQ UNUSED(prev); isc_atomic_xaddq((isc_int64_t *)&stats->counters[counter], 1); #else @@ -227,7 +259,7 @@ incrementcounter(isc_stats_t *stats, int counter) { stats->counters[counter]++; #endif -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS isc_rwlock_unlock(&stats->counterlock, isc_rwlocktype_read); #endif } @@ -236,7 +268,7 @@ static inline void decrementcounter(isc_stats_t *stats, int counter) { isc_int32_t prev; -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS isc_rwlock_lock(&stats->counterlock, isc_rwlocktype_read); #endif @@ -245,7 +277,7 @@ decrementcounter(isc_stats_t *stats, int counter) { if (prev == 0) isc_atomic_xadd((isc_int32_t *)&stats->counters[counter].hi, -1); -#elif defined(ISC_PLATFORM_HAVEXADDQ) +#elif ISC_STATS_HAVEATOMICQ UNUSED(prev); isc_atomic_xaddq((isc_int64_t *)&stats->counters[counter], -1); #else @@ -253,7 +285,7 @@ decrementcounter(isc_stats_t *stats, int counter) { stats->counters[counter]--; #endif -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS isc_rwlock_unlock(&stats->counterlock, isc_rwlocktype_read); #endif } @@ -262,7 +294,7 @@ static void copy_counters(isc_stats_t *stats) { int i; -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS /* * We use a "write" lock before "reading" the statistics counters as * an exclusive lock. @@ -270,19 +302,21 @@ copy_counters(isc_stats_t *stats) { isc_rwlock_lock(&stats->counterlock, isc_rwlocktype_write); #endif -#if ISC_STATS_USEMULTIFIELDS for (i = 0; i < stats->ncounters; i++) { +#if ISC_STATS_USEMULTIFIELDS stats->copiedcounters[i] = - (isc_uint64_t)(stats->counters[i].hi) << 32 | - stats->counters[i].lo; - } + (isc_uint64_t)(stats->counters[i].hi) << 32 | + stats->counters[i].lo; +#elif ISC_STATS_HAVEATOMICQ + /* use xaddq(..., 0) as an atomic load */ + stats->copiedcounters[i] = + (isc_uint64_t)isc_atomic_xaddq((isc_int64_t *)&stats->counters[i], 0); #else - UNUSED(i); - memmove(stats->copiedcounters, stats->counters, - stats->ncounters * sizeof(isc_stat_t)); + stats->copiedcounters[i] = stats->counters[i]; #endif + } -#ifdef ISC_RWLOCK_USEATOMIC +#if ISC_STATS_LOCKCOUNTERS isc_rwlock_unlock(&stats->counterlock, isc_rwlocktype_write); #endif } |