bind9/lib/isc/stats.c

/*
 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * See the COPYRIGHT file distributed with this work for additional
 * information regarding copyright ownership.
 */


/*! \file */

#include <inttypes.h>
#include <string.h>

#include <isc/atomic.h>
#include <isc/buffer.h>
#include <isc/magic.h>
#include <isc/mem.h>
#include <isc/platform.h>
#include <isc/print.h>
#include <isc/refcount.h>
#include <isc/stats.h>
#include <isc/thread.h>
#include <isc/util.h>

#define ISC_STATS_MAGIC			ISC_MAGIC('S', 't', 'a', 't')
#define ISC_STATS_VALID(x)		ISC_MAGIC_VALID(x, ISC_STATS_MAGIC)

#define STATS_BUCKETS 64

#if defined(_WIN32) && !defined(_WIN64)
	typedef atomic_int_fast32_t isc__atomic_statcounter_t;
#else
	typedef atomic_int_fast64_t isc__atomic_statcounter_t;
#endif

struct isc_stats {
	unsigned int			magic;
	isc_mem_t			*mctx;
	isc_refcount_t			references;
	int				ncounters;
	isc__atomic_statcounter_t	*counters;
};

ISC_THREAD_LOCAL int isc__stats_thread_v = -1;
static atomic_uint_fast32_t isc__stats_thread_n = 0;

static int
threadhash() {
	if (isc__stats_thread_v < 0) {
		isc__stats_thread_v = atomic_fetch_add_relaxed(&isc__stats_thread_n, 1) % STATS_BUCKETS;
	}
	return (isc__stats_thread_v);
}

static isc_result_t
create_stats(isc_mem_t *mctx, int ncounters, isc_stats_t **statsp) {
	isc_stats_t *stats;
	size_t counters_alloc_size;

	REQUIRE(statsp != NULL && *statsp == NULL);

	stats = isc_mem_get(mctx, sizeof(*stats));
	counters_alloc_size = sizeof(isc__atomic_statcounter_t) * ncounters * STATS_BUCKETS;
	stats->counters = isc_mem_get(mctx, counters_alloc_size);
	isc_refcount_init(&stats->references, 1);
	memset(stats->counters, 0, counters_alloc_size);
	stats->mctx = NULL;
	isc_mem_attach(mctx, &stats->mctx);
	stats->ncounters = ncounters;
	stats->magic = ISC_STATS_MAGIC;
	*statsp = stats;

	return (ISC_R_SUCCESS);
}

void
isc_stats_attach(isc_stats_t *stats, isc_stats_t **statsp) {
	REQUIRE(ISC_STATS_VALID(stats));
	REQUIRE(statsp != NULL && *statsp == NULL);

	isc_refcount_increment(&stats->references);
	*statsp = stats;
}

void
isc_stats_detach(isc_stats_t **statsp) {
	isc_stats_t *stats;

	REQUIRE(statsp != NULL && ISC_STATS_VALID(*statsp));

	stats = *statsp;
	*statsp = NULL;

	if (isc_refcount_decrement(&stats->references) == 1) {
		isc_refcount_destroy(&stats->references);
		isc_mem_put(stats->mctx, stats->counters,
			    sizeof(isc__atomic_statcounter_t) *
				stats->ncounters *
				STATS_BUCKETS);
		isc_mem_putanddetach(&stats->mctx, stats, sizeof(*stats));
	}
}

int
isc_stats_ncounters(isc_stats_t *stats) {
	REQUIRE(ISC_STATS_VALID(stats));

	return (stats->ncounters);
}

isc_result_t
isc_stats_create(isc_mem_t *mctx, isc_stats_t **statsp, int ncounters) {
	REQUIRE(statsp != NULL && *statsp == NULL);

	return (create_stats(mctx, ncounters, statsp));
}

void
isc_stats_increment(isc_stats_t *stats, isc_statscounter_t counter) {
	REQUIRE(ISC_STATS_VALID(stats));
	REQUIRE(counter < stats->ncounters);
	int idx = threadhash() * stats->ncounters + counter;
	atomic_fetch_add_explicit(&stats->counters[idx], 1,
				  memory_order_relaxed);
}

void
isc_stats_decrement(isc_stats_t *stats, isc_statscounter_t counter) {
	REQUIRE(ISC_STATS_VALID(stats));
	REQUIRE(counter < stats->ncounters);

	int idx = threadhash() * stats->ncounters + counter;
	atomic_fetch_sub_explicit(&stats->counters[idx], 1,
				  memory_order_relaxed);
}

void
isc_stats_dump(isc_stats_t *stats, isc_stats_dumper_t dump_fn,
	       void *arg, unsigned int options)
{
	int i;

	REQUIRE(ISC_STATS_VALID(stats));

	for (i = 0; i < stats->ncounters; i++) {
		uint32_t counter = 0;
		int b;
		for (b = 0; b < STATS_BUCKETS; b++) {
			int idx = stats->ncounters * b + i;
			counter += atomic_load_explicit(&stats->counters[idx],
							memory_order_relaxed);
		}
		if ((options & ISC_STATSDUMP_VERBOSE) == 0 && counter == 0) {
			continue;
		}
		dump_fn((isc_statscounter_t)i, counter, arg);
	}
}

void
isc_stats_set(isc_stats_t *stats, uint64_t val,
	      isc_statscounter_t counter)
{
	int i;

	REQUIRE(ISC_STATS_VALID(stats));
	REQUIRE(counter < stats->ncounters);
	atomic_store_explicit(&stats->counters[counter], val,
			      memory_order_relaxed);
	for (i = 1; i < STATS_BUCKETS; i++) {
		int idx = stats->ncounters * i + counter;
		atomic_store_explicit(&stats->counters[idx], val,
				      memory_order_relaxed);
	}
}

void isc_stats_update_if_greater(isc_stats_t *stats,
				 isc_statscounter_t counter,
				 isc_statscounter_t value)
{
	REQUIRE(ISC_STATS_VALID(stats));
	REQUIRE(counter < stats->ncounters);

	isc_statscounter_t curr_value;
	do {
		curr_value = atomic_load_relaxed(&stats->counters[counter]);
		if (curr_value >= value) {
			break;
		}
	} while (!atomic_compare_exchange_strong(&stats->counters[counter],
						 &curr_value,
						 value));
}

isc_statscounter_t
isc_stats_get_counter(isc_stats_t *stats, isc_statscounter_t counter)
{
	uint32_t value = 0;
	int i;
	REQUIRE(ISC_STATS_VALID(stats));
	REQUIRE(counter < stats->ncounters);

	for (i = 0; i < STATS_BUCKETS; i++) {
		int idx = i * stats->ncounters + counter;
		value += atomic_load_explicit(&stats->counters[idx],
					      memory_order_relaxed);
	}
	return (value);
}