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diff --git a/usr.sbin/pmc/view.cc b/usr.sbin/pmc/view.cc
--- a/usr.sbin/pmc/view.cc
+++ b/usr.sbin/pmc/view.cc
@@ -310,6 +310,7 @@
return;
case PMCLOG_TYPE_PMCATTACH: [[fallthrough]];
case PMCLOG_TYPE_PMCDETACH:
+ case PMCLOG_TYPE_PMCGROUPINHERITMISS:
case PMCLOG_TYPE_USERDATA:
case PMCLOG_TYPE_PROCCSW:
case PMCLOG_TYPE_DROPNOTIFY:
diff --git a/usr.sbin/pmcstat/pmcstat.c b/usr.sbin/pmcstat/pmcstat.c
--- a/usr.sbin/pmcstat/pmcstat.c
+++ b/usr.sbin/pmcstat/pmcstat.c
@@ -151,6 +151,77 @@
*/
#define PMCSTAT_MAX_EVENTS_PER_CYCLE 8
+static uint64_t
+pmcstat_events_per_window(void)
+{
+ uint64_t freq;
+ size_t len;
+ int period_ms;
+
+ len = sizeof(freq);
+ if (sysctlbyname("machdep.tsc_freq", &freq, &len, NULL, 0) != 0)
+ return (0);
+ len = sizeof(period_ms);
+ if (sysctlbyname("kern.hwpmc.mux_period_ms", &period_ms, &len, NULL,
+ 0) != 0 || period_ms <= 0)
+ return (0);
+ return (freq / 1000 * (uint64_t)period_ms *
+ PMCSTAT_MAX_EVENTS_PER_CYCLE);
+}
+
+static void
+pmcstat_warn_long_sampling_periods(uint64_t events_per_window)
+{
+ struct pmc_group_times times;
+ struct pmcstat_ev *ev, *leader;
+ uint32_t nmembers;
+
+ if (events_per_window == 0)
+ return;
+ STAILQ_FOREACH(leader, &args.pa_events, ev_next) {
+ if (leader->ev_groupid == 0 || !leader->ev_is_leader ||
+ !PMC_IS_SAMPLING_MODE(leader->ev_mode))
+ continue;
+ nmembers = 0;
+ if (pmc_group_read(leader->ev_pmcid, &nmembers, NULL,
+ &times) != 0 ||
+ times.pgt_enabled == 0 ||
+ times.pgt_running >= times.pgt_enabled)
+ continue;
+
+ STAILQ_FOREACH(ev, &args.pa_events, ev_next) {
+ if (ev->ev_groupid != leader->ev_groupid ||
+ !PMC_IS_SAMPLING_MODE(ev->ev_mode) ||
+ (uint64_t)ev->ev_count <= events_per_window)
+ continue;
+ warnx(
+"WARNING: \"%s\" samples every %ju events in a multiplexed group, more than\n"
+"one kern.hwpmc.mux_period_ms rotation window can retire; expect few samples\n"
+"or none. Lower -n, or drop the braces to stop multiplexing.",
+ ev->ev_name, (uintmax_t)ev->ev_count);
+ }
+ }
+}
+
+/*
+ * How many times a fork could not carry its group to the child.
+ * A kernel counter that nobody reads gives no insight, so -d
+ * compares this value across the run and reports any change. The
+ * value is zero if the driver does not report it.
+ */
+static uint64_t
+pmcstat_fork_attach_failures(void)
+{
+ uint64_t v;
+ size_t len;
+
+ len = sizeof(v);
+ if (sysctlbyname("kern.hwpmc.stats.group_fork_attach_failures", &v,
+ &len, NULL, 0) != 0)
+ return (0);
+ return (v);
+}
+
void
pmcstat_cleanup(void)
{
@@ -587,6 +658,7 @@
const char *errmsg, *graphfilename;
enum pmcstat_state runstate;
struct pmc_driverstats ds_start, ds_end;
+ uint64_t fork_misses_start, fork_misses_end, events_per_window;
struct pmcstat_ev *ev;
struct sigaction sa;
struct kevent kev;
@@ -1360,6 +1432,8 @@
* Allocate PMCs.
*/
+ events_per_window = pmcstat_events_per_window();
+
STAILQ_FOREACH(ev, &args.pa_events, ev_next) {
int rc;
@@ -1536,7 +1610,10 @@
if (check_driver_stats && pmc_get_driver_stats(&ds_start) < 0)
err(EX_OSERR, "ERROR: Cannot retrieve driver statistics");
- /* Attach process pmcs to the target process. */
+ if (do_descendants)
+ fork_misses_start = pmcstat_fork_attach_failures();
+
+ /* Attach process PMCs to the target process. */
if (args.pa_flags & (FLAG_HAS_TARGET | FLAG_HAS_COMMANDLINE)) {
if (SLIST_EMPTY(&args.pa_targets))
errx(EX_DATAERR,
@@ -1703,6 +1780,8 @@
} while (runstate != PMCSTAT_FINISHED);
+ pmcstat_warn_long_sampling_periods(events_per_window);
+
if ((args.pa_flags & FLAG_DO_TOP) && args.pa_toptty) {
pmcstat_topexit();
args.pa_toptty = 0;
@@ -1714,7 +1793,23 @@
pmcstat_cleanup();
- /* check if the driver lost any samples or events */
+ /*
+ * Report children whose group the driver could not carry
+ * over. Their work is missing from the totals above, which
+ * otherwise look complete.
+ */
+ if (do_descendants) {
+ fork_misses_end = pmcstat_fork_attach_failures();
+ if (fork_misses_end > fork_misses_start)
+ warnx(
+"WARNING: %ju descendant attach%s failed; their contributions are not in\n"
+"these totals.",
+ (uintmax_t)(fork_misses_end - fork_misses_start),
+ (fork_misses_end - fork_misses_start) != 1 ?
+ "es" : "");
+ }
+
+ /* Check if the driver lost any samples or events. */
if (check_driver_stats) {
if (pmc_get_driver_stats(&ds_end) < 0)
err(EX_OSERR,
diff --git a/usr.sbin/pmcstat/pmcstat_log.c b/usr.sbin/pmcstat/pmcstat_log.c
--- a/usr.sbin/pmcstat/pmcstat_log.c
+++ b/usr.sbin/pmcstat/pmcstat_log.c
@@ -573,6 +573,11 @@
ev.pl_u.pl_d.pl_pmcid,
ev.pl_u.pl_d.pl_pid);
break;
+ case PMCLOG_TYPE_PMCGROUPINHERITMISS:
+ PMCSTAT_PRINT_ENTRY("group-inherit-miss","0x%x %d",
+ ev.pl_u.pl_gim.pl_pmcid,
+ ev.pl_u.pl_gim.pl_pid);
+ break;
case PMCLOG_TYPE_PROCCSW:
PMCSTAT_PRINT_ENTRY("cswval","0x%x %d %jd",
ev.pl_u.pl_c.pl_pmcid,

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