- Add a facility similar to LOCK_PROFILING under SLEEPQUEUE_PROFILING. Keep

   a simple (wmesg, count) tuple in a hash to keep track of how many times
   we sleep at each wait message.  We hash on message and not channel.  No
   line number information is given as typically wait messages are not used in
   more than one place.  Identical strings defined at different addresses will
   show up with seperate counters.
 - Use debug.sleepq.enable to enable, .reset to reset, and .stats dumps stats.
 - Do an unsynchronized check in sleepq_switch() prior to switching before
   calling sleepq_profile() which uses a global lock to synchronize the hash.
   Only sleeps which actually cause a context switch are counted.

1 files changed, 159 insertions, 1 deletions

diff --git a/sys/kern/subr_sleepqueue.c b/sys/kern/subr_sleepqueue.c
index 86be815a2bdd..fe3b5e959109 100644
--- a/sys/kern/subr_sleepqueue.c
+++ b/sys/kern/subr_sleepqueue.c
@@ -73,6 +73,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/ktr.h>
 #include <sys/mutex.h>
 #include <sys/proc.h>
+#include <sys/sbuf.h>
 #include <sys/sched.h>
 #include <sys/signalvar.h>
 #include <sys/sleepqueue.h>
@@ -142,6 +143,9 @@ SYSCTL_NODE(_debug_sleepq, OID_AUTO, chains, CTLFLAG_RD, 0,
     "sleepq chain stats");
 SYSCTL_UINT(_debug_sleepq, OID_AUTO, max_depth, CTLFLAG_RD, &sleepq_max_depth,
     0, "maxmimum depth achieved of a single chain");
+
+static void	sleepq_profile(const char *wmesg);
+static int	prof_enabled;
 #endif
 static struct sleepqueue_chain sleepq_chains[SC_TABLESIZE];
 static uma_zone_t sleepq_zone;
@@ -466,7 +470,10 @@ sleepq_switch(void *wchan, int pri)
 		mtx_unlock_spin(&sc->sc_lock);
 		return;		
 	}
-
+#ifdef SLEEPQUEUE_PROFILING
+	if (prof_enabled)
+		sleepq_profile(td->td_wmesg);
+#endif
 	MPASS(td->td_sleepqueue == NULL);
 	sched_sleep(td, pri);
 	thread_lock_set(td, &sc->sc_lock);
@@ -910,6 +917,157 @@ sleepq_abort(struct thread *td, int intrval)
 	sleepq_resume_thread(sq, td, 0);
 }
 
+#ifdef SLEEPQUEUE_PROFILING
+#define	SLEEPQ_PROF_LOCATIONS	1024
+#define	SLEEPQ_SBUFSIZE		(40 * 512)
+struct sleepq_prof {
+	LIST_ENTRY(sleepq_prof) sp_link;
+	const char	*sp_wmesg;
+	long		sp_count;
+};
+
+LIST_HEAD(sqphead, sleepq_prof);
+
+struct sqphead sleepq_prof_free;
+struct sqphead sleepq_hash[SC_TABLESIZE];
+static struct sleepq_prof sleepq_profent[SLEEPQ_PROF_LOCATIONS];
+static struct mtx sleepq_prof_lock;
+MTX_SYSINIT(sleepq_prof_lock, &sleepq_prof_lock, "sleepq_prof", MTX_SPIN);
+
+static void
+sleepq_profile(const char *wmesg)
+{
+	struct sleepq_prof *sp;
+
+	mtx_lock_spin(&sleepq_prof_lock);
+	if (prof_enabled == 0)
+		goto unlock;
+	LIST_FOREACH(sp, &sleepq_hash[SC_HASH(wmesg)], sp_link)
+		if (sp->sp_wmesg == wmesg)
+			goto done;
+	sp = LIST_FIRST(&sleepq_prof_free);
+	if (sp == NULL)
+		goto unlock;
+	sp->sp_wmesg = wmesg;
+	LIST_REMOVE(sp, sp_link);
+	LIST_INSERT_HEAD(&sleepq_hash[SC_HASH(wmesg)], sp, sp_link);
+done:
+	sp->sp_count++;
+unlock:
+	mtx_unlock_spin(&sleepq_prof_lock);
+	return;
+}
+
+static void
+sleepq_prof_reset(void)
+{
+	struct sleepq_prof *sp;
+	int enabled;
+	int i;
+
+	mtx_lock_spin(&sleepq_prof_lock);
+	enabled = prof_enabled;
+	prof_enabled = 0;
+	for (i = 0; i < SC_TABLESIZE; i++)
+		LIST_INIT(&sleepq_hash[i]);
+	LIST_INIT(&sleepq_prof_free);
+	for (i = 0; i < SLEEPQ_PROF_LOCATIONS; i++) {
+		sp = &sleepq_profent[i];
+		sp->sp_wmesg = NULL;
+		sp->sp_count = 0;
+		LIST_INSERT_HEAD(&sleepq_prof_free, sp, sp_link);
+	}
+	prof_enabled = enabled;
+	mtx_unlock_spin(&sleepq_prof_lock);
+}
+
+static int
+enable_sleepq_prof(SYSCTL_HANDLER_ARGS)
+{
+	int error, v;
+
+	v = prof_enabled;
+	error = sysctl_handle_int(oidp, &v, v, req);
+	if (error)
+		return (error);
+	if (req->newptr == NULL)
+		return (error);
+	if (v == prof_enabled)
+		return (0);
+	if (v == 1)
+		sleepq_prof_reset();
+	mtx_lock_spin(&sleepq_prof_lock);
+	prof_enabled = !!v;
+	mtx_unlock_spin(&sleepq_prof_lock);
+
+	return (0);
+}
+
+static int
+reset_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
+{
+	int error, v;
+
+	v = 0;
+	error = sysctl_handle_int(oidp, &v, 0, req);
+	if (error)
+		return (error);
+	if (req->newptr == NULL)
+		return (error);
+	if (v == 0)
+		return (0);
+	sleepq_prof_reset();
+
+	return (0);
+}
+
+static int
+dump_sleepq_prof_stats(SYSCTL_HANDLER_ARGS)
+{
+	static int multiplier = 1;
+	struct sleepq_prof *sp;
+	struct sbuf *sb;
+	int enabled;
+	int error;
+	int i;
+
+retry_sbufops:
+	sb = sbuf_new(NULL, NULL, SLEEPQ_SBUFSIZE * multiplier, SBUF_FIXEDLEN);
+	sbuf_printf(sb, "\nwmesg\tcount\n");
+	enabled = prof_enabled;
+	mtx_lock_spin(&sleepq_prof_lock);
+	prof_enabled = 0;
+	mtx_unlock_spin(&sleepq_prof_lock);
+	for (i = 0; i < SC_TABLESIZE; i++) {
+		LIST_FOREACH(sp, &sleepq_hash[i], sp_link) {
+			sbuf_printf(sb, "%s\t%ld\n",
+			    sp->sp_wmesg, sp->sp_count);
+			if (sbuf_overflowed(sb)) {
+				sbuf_delete(sb);
+				multiplier++;
+				goto retry_sbufops;
+			}
+		}
+	}
+	mtx_lock_spin(&sleepq_prof_lock);
+	prof_enabled = enabled;
+	mtx_unlock_spin(&sleepq_prof_lock);
+
+	sbuf_finish(sb);
+	error = SYSCTL_OUT(req, sbuf_data(sb), sbuf_len(sb) + 1);
+	sbuf_delete(sb);
+	return (error);
+}
+
+SYSCTL_PROC(_debug_sleepq, OID_AUTO, stats, CTLTYPE_STRING | CTLFLAG_RD,
+    NULL, 0, dump_sleepq_prof_stats, "A", "Sleepqueue profiling statistics");
+SYSCTL_PROC(_debug_sleepq, OID_AUTO, reset, CTLTYPE_INT | CTLFLAG_RW,
+    NULL, 0, reset_sleepq_prof_stats, "I",
+    "Reset sleepqueue profiling statistics");
+SYSCTL_PROC(_debug_sleepq, OID_AUTO, enable, CTLTYPE_INT | CTLFLAG_RW,
+    NULL, 0, enable_sleepq_prof, "I", "Enable sleepqueue profiling");
+#endif
+
 #ifdef DDB
 DB_SHOW_COMMAND(sleepq, db_show_sleepqueue)
 {