mirror of
https://github.com/openvswitch/ovs
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bc0d88eece
When profiling CPU usage in situations involving high numbers of ports, coverage_clear() was highlighted as a commonly called function. It appears that it can be quite expensive to access all of the per-thread coverage counters when threads are constantly waking up. This patch makes each thread only do coverage_clear() logic roughly once per second by introducing per-thread timers. Upcall handler counters may become less accurate, as these threads may sleep without synchronising and not wake up for some time. When the main thread is under load at ~90% CPU, this drops to ~85%. Upcall handler threads sitting at ~2.5% drop to ~1.5%. Signed-off-by: Joe Stringer <joestringer@nicira.com> Signed-off-by: Ben Pfaff <blp@nicira.com>
372 lines
12 KiB
C
372 lines
12 KiB
C
/*
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* Copyright (c) 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <config.h>
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#include "coverage.h"
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#include <inttypes.h>
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#include <stdlib.h>
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#include "dynamic-string.h"
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#include "hash.h"
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#include "svec.h"
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#include "timeval.h"
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#include "unixctl.h"
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#include "util.h"
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#include "vlog.h"
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VLOG_DEFINE_THIS_MODULE(coverage);
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/* The coverage counters. */
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#if USE_LINKER_SECTIONS
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extern struct coverage_counter *__start_coverage[];
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extern struct coverage_counter *__stop_coverage[];
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#define coverage_counters __start_coverage
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#define n_coverage_counters (__stop_coverage - __start_coverage)
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#else /* !USE_LINKER_SECTIONS */
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#define COVERAGE_COUNTER(COUNTER) \
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DECLARE_EXTERN_PER_THREAD_DATA(unsigned int, \
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counter_##COUNTER); \
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DEFINE_EXTERN_PER_THREAD_DATA(counter_##COUNTER, 0); \
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static unsigned int COUNTER##_count(void) \
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{ \
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unsigned int *countp = counter_##COUNTER##_get(); \
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unsigned int count = *countp; \
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*countp = 0; \
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return count; \
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} \
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extern struct coverage_counter counter_##COUNTER; \
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struct coverage_counter counter_##COUNTER \
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= { #COUNTER, COUNTER##_count, 0 };
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#include "coverage.def"
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#undef COVERAGE_COUNTER
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extern struct coverage_counter *coverage_counters[];
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struct coverage_counter *coverage_counters[] = {
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#define COVERAGE_COUNTER(NAME) &counter_##NAME,
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#include "coverage.def"
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#undef COVERAGE_COUNTER
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};
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#define n_coverage_counters ARRAY_SIZE(coverage_counters)
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#endif /* !USE_LINKER_SECTIONS */
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static struct ovs_mutex coverage_mutex = OVS_MUTEX_INITIALIZER;
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DEFINE_STATIC_PER_THREAD_DATA(long long int, coverage_clear_time, LLONG_MIN);
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static long long int coverage_run_time = LLONG_MIN;
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/* Index counter used to compute the moving average array's index. */
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static unsigned int idx_count = 0;
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static void coverage_read(struct svec *);
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static unsigned int coverage_array_sum(const unsigned int *arr,
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const unsigned int len);
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static void
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coverage_unixctl_show(struct unixctl_conn *conn, int argc OVS_UNUSED,
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const char *argv[] OVS_UNUSED, void *aux OVS_UNUSED)
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{
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struct svec lines;
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char *reply;
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svec_init(&lines);
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coverage_read(&lines);
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reply = svec_join(&lines, "\n", "\n");
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unixctl_command_reply(conn, reply);
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free(reply);
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svec_destroy(&lines);
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}
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void
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coverage_init(void)
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{
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unixctl_command_register("coverage/show", "", 0, 0,
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coverage_unixctl_show, NULL);
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}
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/* Sorts coverage counters in descending order by total, within equal
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* totals alphabetically by name. */
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static int
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compare_coverage_counters(const void *a_, const void *b_)
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{
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const struct coverage_counter *const *ap = a_;
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const struct coverage_counter *const *bp = b_;
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const struct coverage_counter *a = *ap;
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const struct coverage_counter *b = *bp;
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if (a->total != b->total) {
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return a->total < b->total ? 1 : -1;
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} else {
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return strcmp(a->name, b->name);
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}
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}
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static uint32_t
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coverage_hash(void)
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{
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struct coverage_counter **c;
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uint32_t hash = 0;
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int n_groups, i;
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/* Sort coverage counters into groups with equal totals. */
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c = xmalloc(n_coverage_counters * sizeof *c);
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ovs_mutex_lock(&coverage_mutex);
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for (i = 0; i < n_coverage_counters; i++) {
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c[i] = coverage_counters[i];
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}
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ovs_mutex_unlock(&coverage_mutex);
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qsort(c, n_coverage_counters, sizeof *c, compare_coverage_counters);
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/* Hash the names in each group along with the rank. */
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n_groups = 0;
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for (i = 0; i < n_coverage_counters; ) {
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int j;
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if (!c[i]->total) {
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break;
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}
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n_groups++;
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hash = hash_int(i, hash);
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for (j = i; j < n_coverage_counters; j++) {
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if (c[j]->total != c[i]->total) {
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break;
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}
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hash = hash_string(c[j]->name, hash);
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}
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i = j;
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}
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free(c);
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return hash_int(n_groups, hash);
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}
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static bool
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coverage_hit(uint32_t hash)
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{
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enum { HIT_BITS = 1024, BITS_PER_WORD = 32 };
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static uint32_t hit[HIT_BITS / BITS_PER_WORD];
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BUILD_ASSERT_DECL(IS_POW2(HIT_BITS));
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static long long int next_clear = LLONG_MIN;
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unsigned int bit_index = hash & (HIT_BITS - 1);
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unsigned int word_index = bit_index / BITS_PER_WORD;
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unsigned int word_mask = 1u << (bit_index % BITS_PER_WORD);
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/* Expire coverage hash suppression once a day. */
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if (time_msec() >= next_clear) {
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memset(hit, 0, sizeof hit);
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next_clear = time_msec() + 60 * 60 * 24 * 1000LL;
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}
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if (hit[word_index] & word_mask) {
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return true;
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} else {
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hit[word_index] |= word_mask;
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return false;
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}
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}
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/* Logs the coverage counters, unless a similar set of events has already been
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* logged.
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*
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* This function logs at log level VLL_INFO. Use care before adjusting this
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* level, because depending on its configuration, syslogd can write changes
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* synchronously, which can cause the coverage messages to take several seconds
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* to write. */
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void
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coverage_log(void)
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{
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static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 3);
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if (!VLOG_DROP_INFO(&rl)) {
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uint32_t hash = coverage_hash();
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if (coverage_hit(hash)) {
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VLOG_INFO("Skipping details of duplicate event coverage for "
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"hash=%08"PRIx32, hash);
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} else {
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struct svec lines;
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const char *line;
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size_t i;
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svec_init(&lines);
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coverage_read(&lines);
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SVEC_FOR_EACH (i, line, &lines) {
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VLOG_INFO("%s", line);
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}
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svec_destroy(&lines);
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}
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}
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}
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/* Adds coverage counter information to 'lines'. */
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static void
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coverage_read(struct svec *lines)
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{
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struct coverage_counter **c = coverage_counters;
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unsigned long long int *totals;
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size_t n_never_hit;
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uint32_t hash;
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size_t i;
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hash = coverage_hash();
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n_never_hit = 0;
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svec_add_nocopy(lines,
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xasprintf("Event coverage, avg rate over last: %d "
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"seconds, last minute, last hour, "
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"hash=%08"PRIx32":",
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COVERAGE_RUN_INTERVAL/1000, hash));
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totals = xmalloc(n_coverage_counters * sizeof *totals);
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ovs_mutex_lock(&coverage_mutex);
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for (i = 0; i < n_coverage_counters; i++) {
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totals[i] = c[i]->total;
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}
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ovs_mutex_unlock(&coverage_mutex);
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for (i = 0; i < n_coverage_counters; i++) {
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if (totals[i]) {
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/* Shows the averaged per-second rates for the last
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* COVERAGE_RUN_INTERVAL interval, the last minute and
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* the last hour. */
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svec_add_nocopy(lines,
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xasprintf("%-24s %5.1f/sec %9.3f/sec "
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"%13.4f/sec total: %llu",
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c[i]->name,
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(c[i]->min[(idx_count - 1) % MIN_AVG_LEN]
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* 1000.0 / COVERAGE_RUN_INTERVAL),
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coverage_array_sum(c[i]->min, MIN_AVG_LEN) / 60.0,
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coverage_array_sum(c[i]->hr, HR_AVG_LEN) / 3600.0,
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totals[i]));
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} else {
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n_never_hit++;
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}
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}
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svec_add_nocopy(lines, xasprintf("%zu events never hit", n_never_hit));
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free(totals);
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}
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/* Runs approximately every COVERAGE_CLEAR_INTERVAL amount of time to
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* synchronize per-thread counters with global counters. Every thread maintains
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* a separate timer to ensure all counters are periodically aggregated. */
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void
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coverage_clear(void)
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{
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long long int now, *thread_time;
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now = time_msec();
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thread_time = coverage_clear_time_get();
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/* Initialize the coverage_clear_time. */
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if (*thread_time == LLONG_MIN) {
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*thread_time = now + COVERAGE_CLEAR_INTERVAL;
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}
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if (now >= *thread_time) {
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size_t i;
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ovs_mutex_lock(&coverage_mutex);
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for (i = 0; i < n_coverage_counters; i++) {
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struct coverage_counter *c = coverage_counters[i];
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c->total += c->count();
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}
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ovs_mutex_unlock(&coverage_mutex);
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*thread_time = now + COVERAGE_CLEAR_INTERVAL;
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}
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}
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/* Runs approximately every COVERAGE_RUN_INTERVAL amount of time to update the
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* coverage counters' 'min' and 'hr' array. 'min' array is for cumulating
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* per second counts into per minute count. 'hr' array is for cumulating per
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* minute counts into per hour count. Every thread may call this function. */
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void
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coverage_run(void)
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{
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/* Defines the moving average array index variables. */
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static unsigned int min_idx, hr_idx;
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struct coverage_counter **c = coverage_counters;
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long long int now;
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ovs_mutex_lock(&coverage_mutex);
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now = time_msec();
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/* Initialize the coverage_run_time. */
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if (coverage_run_time == LLONG_MIN) {
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coverage_run_time = now + COVERAGE_RUN_INTERVAL;
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}
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if (now >= coverage_run_time) {
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size_t i, j;
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/* Computes the number of COVERAGE_RUN_INTERVAL slots, since
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* it is possible that the actual run interval is multiple of
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* COVERAGE_RUN_INTERVAL. */
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int slots = (now - coverage_run_time) / COVERAGE_RUN_INTERVAL + 1;
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for (i = 0; i < n_coverage_counters; i++) {
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unsigned int count, portion;
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unsigned int m_idx = min_idx;
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unsigned int h_idx = hr_idx;
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unsigned int idx = idx_count;
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/* Computes the differences between the current total and the one
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* recorded in last invocation of coverage_run(). */
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count = c[i]->total - c[i]->last_total;
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c[i]->last_total = c[i]->total;
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/* The count over the time interval is evenly distributed
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* among slots by calculating the portion. */
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portion = count / slots;
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for (j = 0; j < slots; j++) {
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/* Updates the index variables. */
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/* The m_idx is increased from 0 to MIN_AVG_LEN - 1. Every
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* time the m_idx finishes a cycle (a cycle is one minute),
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* the h_idx is incremented by 1. */
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m_idx = idx % MIN_AVG_LEN;
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h_idx = idx / MIN_AVG_LEN;
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c[i]->min[m_idx] = portion + (j == (slots - 1)
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? count % slots : 0);
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c[i]->hr[h_idx] = m_idx == 0
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? c[i]->min[m_idx]
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: (c[i]->hr[h_idx] + c[i]->min[m_idx]);
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/* This is to guarantee that h_idx ranges from 0 to 59. */
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idx = (idx + 1) % (MIN_AVG_LEN * HR_AVG_LEN);
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}
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}
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/* Updates the global index variables. */
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idx_count = (idx_count + slots) % (MIN_AVG_LEN * HR_AVG_LEN);
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min_idx = idx_count % MIN_AVG_LEN;
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hr_idx = idx_count / MIN_AVG_LEN;
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/* Updates the run time. */
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coverage_run_time = now + COVERAGE_RUN_INTERVAL;
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}
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ovs_mutex_unlock(&coverage_mutex);
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}
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static unsigned int
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coverage_array_sum(const unsigned int *arr, const unsigned int len)
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{
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unsigned int sum = 0;
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size_t i;
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ovs_mutex_lock(&coverage_mutex);
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for (i = 0; i < len; i++) {
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sum += arr[i];
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}
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ovs_mutex_unlock(&coverage_mutex);
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return sum;
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}
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