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simplify the isc_stat structure to take avantage of atomics

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This commit is contained in:
Evan Hunt 2019-02-07 19:41:43 -08:00
parent 8aac8358ec
commit 4e5edb35e4
1 changed files with 16 additions and 81 deletions
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97
lib/isc/stats.c
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@ -21,7 +21,7 @@
#include <isc/mem.h>
#include <isc/platform.h>
#include <isc/print.h>
#include <isc/rwlock.h>
#include <isc/refcount.h>
#include <isc/stats.h>
#include <isc/util.h>
@ -31,78 +31,30 @@
typedef atomic_int_fast64_t isc_stat_t;
struct isc_stats {
/*% Unlocked */
unsigned int magic;
isc_mem_t *mctx;
int ncounters;
isc_mutex_t lock;
unsigned int references; /* locked by lock */
/*%
* Locked by counterlock or unlocked if efficient rwlock is not
* available.
*/
isc_stat_t *counters;
/*%
* We don't want to lock the counters while we are dumping, so we first
* copy the current counter values into a local array. This buffer
* will be used as the copy destination. It's allocated on creation
* of the stats structure so that the dump operation won't fail due
* to memory allocation failure.
* XXX: this approach is weird for non-threaded build because the
* additional memory and the copy overhead could be avoided. We prefer
* simplicity here, however, under the assumption that this function
* should be only rarely called.
*/
uint64_t *copiedcounters;
unsigned int magic;
isc_mem_t *mctx;
isc_refcount_t refs;
int ncounters;
isc_stat_t *counters;
};
static isc_result_t
create_stats(isc_mem_t *mctx, int ncounters, isc_stats_t **statsp) {
isc_stats_t *stats;
isc_result_t result = ISC_R_SUCCESS;
REQUIRE(statsp != NULL && *statsp == NULL);
stats = isc_mem_get(mctx, sizeof(*stats));
if (stats == NULL)
return (ISC_R_NOMEMORY);
isc_mutex_init(&stats->lock);
stats->counters = isc_mem_get(mctx, sizeof(isc_stat_t) * ncounters);
if (stats->counters == NULL) {
result = ISC_R_NOMEMORY;
goto clean_mutex;
}
stats->copiedcounters = isc_mem_get(mctx,
sizeof(uint64_t) * ncounters);
if (stats->copiedcounters == NULL) {
result = ISC_R_NOMEMORY;
goto clean_counters;
}
stats->references = 1;
isc_refcount_init(&stats->refs, 1);
memset(stats->counters, 0, sizeof(isc_stat_t) * ncounters);
stats->mctx = NULL;
isc_mem_attach(mctx, &stats->mctx);
stats->ncounters = ncounters;
stats->magic = ISC_STATS_MAGIC;
*statsp = stats;
return (result);
clean_counters:
isc_mem_put(mctx, stats->counters, sizeof(isc_stat_t) * ncounters);
clean_mutex:
isc_mutex_destroy(&stats->lock);
isc_mem_put(mctx, stats, sizeof(*stats));
return (result);
return (ISC_R_SUCCESS);
}
void
@ -110,10 +62,7 @@ isc_stats_attach(isc_stats_t *stats, isc_stats_t **statsp) {
REQUIRE(ISC_STATS_VALID(stats));
REQUIRE(statsp != NULL && *statsp == NULL);
LOCK(&stats->lock);
stats->references++;
UNLOCK(&stats->lock);
isc_refcount_increment(&stats->refs);
*statsp = stats;
}
@ -126,21 +75,11 @@ isc_stats_detach(isc_stats_t **statsp) {
stats = *statsp;
*statsp = NULL;
LOCK(&stats->lock);
stats->references--;
if (stats->references == 0) {
isc_mem_put(stats->mctx, stats->copiedcounters,
sizeof(isc_stat_t) * stats->ncounters);
if (isc_refcount_decrement(&stats->refs) == 1) {
isc_mem_put(stats->mctx, stats->counters,
sizeof(isc_stat_t) * stats->ncounters);
UNLOCK(&stats->lock);
isc_mutex_destroy(&stats->lock);
isc_mem_putanddetach(&stats->mctx, stats, sizeof(*stats));
return;
}
UNLOCK(&stats->lock);
}
int
@ -184,16 +123,12 @@ isc_stats_dump(isc_stats_t *stats, isc_stats_dumper_t dump_fn,
REQUIRE(ISC_STATS_VALID(stats));
for (i = 0; i < stats->ncounters; i++) {
stats->copiedcounters[i] =
atomic_load_explicit(&stats->counters[i],
memory_order_relaxed);
}
for (i = 0; i < stats->ncounters; i++) {
if ((options & ISC_STATSDUMP_VERBOSE) == 0 &&
stats->copiedcounters[i] == 0)
continue;
dump_fn((isc_statscounter_t)i, stats->copiedcounters[i], arg);
uint32_t counter = atomic_load_explicit(&stats->counters[i],
memory_order_relaxed);
if ((options & ISC_STATSDUMP_VERBOSE) == 0 && counter == 0) {
continue;
}
dump_fn((isc_statscounter_t)i, counter, arg);
}
}