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poll-loop: Automatically log reason for wakeup when CPU usage spikes.

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For a long time, the poll-loop module has had the ability to log the reason
for wakeups, which is valuable for debugging excessive use of CPU time.
But I have to ask users to turn up the log level for the module, which
wastes their time and mine.  This commit improves the situation by
automatically logging the reason for a wakeup whenever a process's
estimated CPU usage rises above 50%.  (ovs-vswitchd often uses less than
1% CPU; more than 5% CPU is uncommon.)
This commit is contained in:
Ben Pfaff
2011-05-24 12:23:42 -07:00
parent 3a88e544e0
commit 959ec62e32
3 changed files with 120 additions and 31 deletions
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84
lib/poll-loop.c
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@@ -146,23 +146,65 @@ poll_immediate_wake(const char *where)
poll_timer_wait(0, where);
}
static void PRINTF_FORMAT(2, 3)
log_wakeup(const char *where, const char *format, ...)
/* Logs, if appropriate, that the poll loop was awakened by an event
* registered at 'where' (typically a source file and line number). The other
* arguments have two possible interpretations:
*
* - If 'pollfd' is nonnull then it should be the "struct pollfd" that caused
* the wakeup. In this case, 'timeout' is ignored.
*
* - If 'pollfd' is nonnull then 'timeout' is the number of milliseconds
* after which the poll loop woke up.
*/
static void
log_wakeup(const char *where, const struct pollfd *pollfd, int timeout)
{
struct ds ds;
va_list args;
static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(120, 120);
enum vlog_level level;
int cpu_usage;
struct ds s;
ds_init(&ds);
va_start(args, format);
ds_put_format_valist(&ds, format, args);
va_end(args);
if (where) {
ds_put_format(&ds, " at %s", where);
cpu_usage = get_cpu_usage();
if (VLOG_IS_DBG_ENABLED()) {
level = VLL_DBG;
} else if (cpu_usage > 50 && !VLOG_DROP_WARN(&rl)) {
level = VLL_WARN;
} else {
return;
}
VLOG_DBG("%s", ds_cstr(&ds));
ds_destroy(&ds);
ds_init(&s);
ds_put_cstr(&s, "wakeup due to ");
if (pollfd) {
char *description = describe_fd(pollfd->fd);
if (pollfd->revents & POLLIN) {
ds_put_cstr(&s, "[POLLIN]");
}
if (pollfd->revents & POLLOUT) {
ds_put_cstr(&s, "[POLLOUT]");
}
if (pollfd->revents & POLLERR) {
ds_put_cstr(&s, "[POLLERR]");
}
if (pollfd->revents & POLLHUP) {
ds_put_cstr(&s, "[POLLHUP]");
}
if (pollfd->revents & POLLNVAL) {
ds_put_cstr(&s, "[POLLNVAL]");
}
ds_put_format(&s, " on fd %d (%s)", pollfd->fd, description);
free(description);
} else {
ds_put_format(&s, "%d-ms timeout", timeout);
}
if (where) {
ds_put_format(&s, " at %s", where);
}
if (cpu_usage >= 0) {
ds_put_format(&s, " (%d%% CPU usage)", cpu_usage);
}
VLOG(level, "%s", ds_cstr(&s));
ds_destroy(&s);
}
/* Blocks until one or more of the events registered with poll_fd_wait()
@@ -203,21 +245,13 @@ poll_block(void)
if (retval < 0) {
static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
VLOG_ERR_RL(&rl, "poll: %s", strerror(-retval));
} else if (!retval && VLOG_IS_DBG_ENABLED()) {
log_wakeup(timeout_where, "%d-ms timeout", timeout);
} else if (!retval) {
log_wakeup(timeout_where, NULL, timeout);
}
LIST_FOR_EACH_SAFE (pw, next, node, &waiters) {
if (pw->pollfd->revents && VLOG_IS_DBG_ENABLED()) {
char *description = describe_fd(pw->fd);
log_wakeup(pw->where, "%s%s%s%s%s on fd %d (%s)",
pw->pollfd->revents & POLLIN ? "[POLLIN]" : "",
pw->pollfd->revents & POLLOUT ? "[POLLOUT]" : "",
pw->pollfd->revents & POLLERR ? "[POLLERR]" : "",
pw->pollfd->revents & POLLHUP ? "[POLLHUP]" : "",
pw->pollfd->revents & POLLNVAL ? "[POLLNVAL]" : "",
pw->fd, description);
free(description);
if (pw->pollfd->revents) {
log_wakeup(pw->where, pw->pollfd, 0);
}
poll_cancel(pw);
}