diff --git a/include/jemalloc/internal/mutex_inlines.h b/include/jemalloc/internal/mutex_inlines.h
index cf0ce23a..8e81fcde 100644
--- a/include/jemalloc/internal/mutex_inlines.h
+++ b/include/jemalloc/internal/mutex_inlines.h
@@ -9,6 +9,9 @@ bool	malloc_mutex_trylock(malloc_mutex_t *mutex);
 void	malloc_mutex_unlock(tsdn_t *tsdn, malloc_mutex_t *mutex);
 void	malloc_mutex_assert_owner(tsdn_t *tsdn, malloc_mutex_t *mutex);
 void	malloc_mutex_assert_not_owner(tsdn_t *tsdn, malloc_mutex_t *mutex);
+void	malloc_lock_prof_read(tsdn_t *tsdn, lock_prof_data_t *data,
+    malloc_mutex_t *mutex);
+void	malloc_lock_prof_merge(lock_prof_data_t *sum, lock_prof_data_t *data);
 #endif
 
 #if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_MUTEX_C_))
@@ -23,6 +26,24 @@ malloc_mutex_trylock(malloc_mutex_t *mutex) {
 	return MALLOC_MUTEX_TRYLOCK(mutex);
 }
 
+/* Aggregate lock prof data. */
+JEMALLOC_INLINE void
+malloc_lock_prof_merge(lock_prof_data_t *sum, lock_prof_data_t *data) {
+	nstime_add(&sum->tot_wait_time, &data->tot_wait_time);
+	if (nstime_compare(&data->max_wait_time, &sum->max_wait_time)) {
+		nstime_copy(&sum->max_wait_time, &data->max_wait_time);
+	}
+	sum->n_wait_times += data->n_wait_times;
+	sum->n_spin_acquired += data->n_spin_acquired;
+
+	if (sum->max_n_thds < data->max_n_thds) {
+		sum->max_n_thds = data->max_n_thds;
+	}
+	sum->n_waiting_thds += data->n_waiting_thds;
+	sum->n_owner_switches += data->n_owner_switches;
+	sum->n_lock_ops += data->n_lock_ops;
+}
+
 JEMALLOC_INLINE void
 malloc_mutex_lock(tsdn_t *tsdn, malloc_mutex_t *mutex) {
 	witness_assert_not_owner(tsdn, &mutex->witness);
@@ -58,6 +79,20 @@ JEMALLOC_INLINE void
 malloc_mutex_assert_not_owner(tsdn_t *tsdn, malloc_mutex_t *mutex) {
 	witness_assert_not_owner(tsdn, &mutex->witness);
 }
+
+/* Copy the prof data from mutex for processing. */
+JEMALLOC_INLINE void
+malloc_lock_prof_read(tsdn_t *tsdn, lock_prof_data_t *data,
+    malloc_mutex_t *mutex) {
+	lock_prof_data_t *source = &mutex->prof_data;
+	/* Can only read with the lock. */
+	malloc_mutex_assert_owner(tsdn, mutex);
+
+	*data = *source;
+	/* n_wait_thds is not reported (modified w/o locking). */
+	data->n_waiting_thds = 0;
+}
+
 #endif
 
 #endif /* JEMALLOC_INTERNAL_MUTEX_INLINES_H */
diff --git a/include/jemalloc/internal/nstime_externs.h b/include/jemalloc/internal/nstime_externs.h
index cf14ae0c..1abc84d9 100644
--- a/include/jemalloc/internal/nstime_externs.h
+++ b/include/jemalloc/internal/nstime_externs.h
@@ -5,6 +5,7 @@ void	nstime_init(nstime_t *time, uint64_t ns);
 void	nstime_init2(nstime_t *time, uint64_t sec, uint64_t nsec);
 uint64_t	nstime_ns(const nstime_t *time);
 uint64_t	nstime_sec(const nstime_t *time);
+uint64_t	nstime_msec(const nstime_t *time);
 uint64_t	nstime_nsec(const nstime_t *time);
 void	nstime_copy(nstime_t *time, const nstime_t *source);
 int	nstime_compare(const nstime_t *a, const nstime_t *b);
diff --git a/include/jemalloc/internal/private_symbols.txt b/include/jemalloc/internal/private_symbols.txt
index e138de0c..14ecdeda 100644
--- a/include/jemalloc/internal/private_symbols.txt
+++ b/include/jemalloc/internal/private_symbols.txt
@@ -273,6 +273,7 @@ malloc_mutex_assert_owner
 malloc_mutex_boot
 malloc_mutex_init
 malloc_mutex_lock
+malloc_mutex_lock_slow
 malloc_mutex_postfork_child
 malloc_mutex_postfork_parent
 malloc_mutex_prefork
@@ -302,6 +303,7 @@ nstime_imultiply
 nstime_init
 nstime_init2
 nstime_monotonic
+nstime_msec
 nstime_ns
 nstime_nsec
 nstime_sec
diff --git a/include/jemalloc/internal/stats_structs.h b/include/jemalloc/internal/stats_structs.h
index ffcb3c18..cbc448a3 100644
--- a/include/jemalloc/internal/stats_structs.h
+++ b/include/jemalloc/internal/stats_structs.h
@@ -56,6 +56,8 @@ struct malloc_bin_stats_s {
 
 	/* Current number of slabs in this bin. */
 	size_t		curslabs;
+
+	lock_prof_data_t lock_data;
 };
 
 struct malloc_large_stats_s {
diff --git a/src/arena.c b/src/arena.c
index ef7ec37b..832a125e 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -299,6 +299,7 @@ arena_stats_merge(tsdn_t *tsdn, arena_t *arena, unsigned *nthreads,
 		arena_bin_t *bin = &arena->bins[i];
 
 		malloc_mutex_lock(tsdn, &bin->lock);
+		malloc_lock_prof_read(tsdn, &bstats[i].lock_data, &bin->lock);
 		bstats[i].nmalloc += bin->stats.nmalloc;
 		bstats[i].ndalloc += bin->stats.ndalloc;
 		bstats[i].nrequests += bin->stats.nrequests;
diff --git a/src/ctl.c b/src/ctl.c
index ee69be6d..d9f8be60 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -145,6 +145,7 @@ CTL_PROTO(stats_arenas_i_bins_j_nflushes)
 CTL_PROTO(stats_arenas_i_bins_j_nslabs)
 CTL_PROTO(stats_arenas_i_bins_j_nreslabs)
 CTL_PROTO(stats_arenas_i_bins_j_curslabs)
+CTL_PROTO(stats_arenas_i_bins_j_lock_data)
 INDEX_PROTO(stats_arenas_i_bins_j)
 CTL_PROTO(stats_arenas_i_lextents_j_nmalloc)
 CTL_PROTO(stats_arenas_i_lextents_j_ndalloc)
@@ -357,7 +358,8 @@ static const ctl_named_node_t stats_arenas_i_bins_j_node[] = {
 	{NAME("nflushes"),	CTL(stats_arenas_i_bins_j_nflushes)},
 	{NAME("nslabs"),	CTL(stats_arenas_i_bins_j_nslabs)},
 	{NAME("nreslabs"),	CTL(stats_arenas_i_bins_j_nreslabs)},
-	{NAME("curslabs"),	CTL(stats_arenas_i_bins_j_curslabs)}
+	{NAME("curslabs"),	CTL(stats_arenas_i_bins_j_curslabs)},
+	{NAME("lock_data"),	CTL(stats_arenas_i_bins_j_lock_data)}
 };
 static const ctl_named_node_t super_stats_arenas_i_bins_j_node[] = {
 	{NAME(""),		CHILD(named, stats_arenas_i_bins_j)}
@@ -726,6 +728,8 @@ ctl_arena_stats_sdmerge(ctl_arena_t *ctl_sdarena, ctl_arena_t *ctl_arena,
 			} else {
 				assert(astats->bstats[i].curslabs == 0);
 			}
+			malloc_lock_prof_merge(&sdstats->bstats[i].lock_data,
+			    &astats->bstats[i].lock_data);
 		}
 
 		for (i = 0; i < NSIZES - NBINS; i++) {
@@ -2333,6 +2337,8 @@ CTL_RO_CGEN(config_stats, stats_arenas_i_bins_j_nreslabs,
     arenas_i(mib[2])->astats->bstats[mib[4]].reslabs, uint64_t)
 CTL_RO_CGEN(config_stats, stats_arenas_i_bins_j_curslabs,
     arenas_i(mib[2])->astats->bstats[mib[4]].curslabs, size_t)
+CTL_RO_CGEN(config_stats, stats_arenas_i_bins_j_lock_data,
+    arenas_i(mib[2])->astats->bstats[mib[4]].lock_data, lock_prof_data_t)
 
 static const ctl_named_node_t *
 stats_arenas_i_bins_j_index(tsdn_t *tsdn, const size_t *mib, size_t miblen,
diff --git a/src/nstime.c b/src/nstime.c
index a3f6c1de..70b2f9d8 100644
--- a/src/nstime.c
+++ b/src/nstime.c
@@ -1,6 +1,7 @@
 #include "jemalloc/internal/jemalloc_internal.h"
 
 #define BILLION	UINT64_C(1000000000)
+#define MILLION	UINT64_C(1000000)
 
 void
 nstime_init(nstime_t *time, uint64_t ns) {
@@ -17,6 +18,11 @@ nstime_ns(const nstime_t *time) {
 	return time->ns;
 }
 
+uint64_t
+nstime_msec(const nstime_t *time) {
+	return time->ns / MILLION;
+}
+
 uint64_t
 nstime_sec(const nstime_t *time) {
 	return time->ns / BILLION;
diff --git a/src/stats.c b/src/stats.c
index 58b9a04f..58283f87 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -32,6 +32,31 @@ bool	opt_stats_print = false;
 
 /******************************************************************************/
 
+/* Calculate x.yyy and output a string (takes a fixed sized char array). */
+static bool
+get_rate_str(uint64_t dividend, uint64_t divisor, char str[6]) {
+	if (divisor == 0 || dividend > divisor) {
+		/* The rate is not supposed to be greater than 1. */
+		return true;
+	}
+	if (dividend > 0) {
+		assert(UINT64_MAX / dividend >= 1000);
+	}
+
+	unsigned n = (unsigned)((dividend * 1000) / divisor);
+	if (n < 10) {
+		malloc_snprintf(str, 6, "0.00%u", n);
+	} else if (n < 100) {
+		malloc_snprintf(str, 6, "0.0%u", n);
+	} else if (n < 1000) {
+		malloc_snprintf(str, 6, "0.%u", n);
+	} else {
+		malloc_snprintf(str, 6, "1");
+	}
+
+	return false;
+}
+
 static void
 stats_arena_bins_print(void (*write_cb)(void *, const char *), void *cbopaque,
     bool json, bool large, unsigned i) {
@@ -51,13 +76,14 @@ stats_arena_bins_print(void (*write_cb)(void *, const char *), void *cbopaque,
 			    "bins:           size ind    allocated      nmalloc"
 			    "      ndalloc    nrequests      curregs"
 			    "     curslabs regs pgs  util       nfills"
-			    "     nflushes     newslabs      reslabs\n");
+			    "     nflushes     newslabs      reslabs"
+			    "   contention     max_wait\n");
 		} else {
 			malloc_cprintf(write_cb, cbopaque,
 			    "bins:           size ind    allocated      nmalloc"
 			    "      ndalloc    nrequests      curregs"
 			    "     curslabs regs pgs  util     newslabs"
-			    "      reslabs\n");
+			    "      reslabs   contention     max_wait\n");
 		}
 	}
 	for (j = 0, in_gap = false; j < nbins; j++) {
@@ -100,6 +126,9 @@ stats_arena_bins_print(void (*write_cb)(void *, const char *), void *cbopaque,
 		    uint64_t);
 		CTL_M2_M4_GET("stats.arenas.0.bins.0.curslabs", i, j, &curslabs,
 		    size_t);
+		lock_prof_data_t lock_data;
+		CTL_M2_M4_GET("stats.arenas.0.bins.0.lock_data", i, j,
+		    &lock_data, lock_prof_data_t);
 
 		if (json) {
 			malloc_cprintf(write_cb, cbopaque,
@@ -127,55 +156,59 @@ stats_arena_bins_print(void (*write_cb)(void *, const char *), void *cbopaque,
 			    curslabs,
 			    (j + 1 < nbins) ? "," : "");
 		} else if (!in_gap) {
-			size_t availregs, milli;
-			char util[6]; /* "x.yyy". */
-
-			availregs = nregs * curslabs;
-			milli = (availregs != 0) ? (1000 * curregs) / availregs
-			    : 1000;
-
-			if (milli > 1000) {
-				/*
-				 * Race detected: the counters were read in
-				 * separate mallctl calls and concurrent
-				 * operations happened in between. In this case
-				 * no meaningful utilization can be computed.
-				 */
-				malloc_snprintf(util, sizeof(util), " race");
-			} else if (milli < 10) {
-				malloc_snprintf(util, sizeof(util),
-				    "0.00%zu", milli);
-			} else if (milli < 100) {
-				malloc_snprintf(util, sizeof(util), "0.0%zu",
-				    milli);
-			} else if (milli < 1000) {
-				malloc_snprintf(util, sizeof(util), "0.%zu",
-				    milli);
-			} else {
-				assert(milli == 1000);
-				malloc_snprintf(util, sizeof(util), "1");
+			size_t availregs = nregs * curslabs;
+			char util[6];
+			if (get_rate_str((uint64_t)curregs, (uint64_t)availregs,
+			    util)) {
+				if (availregs == 0) {
+					malloc_snprintf(util, sizeof(util),
+					    "1");
+				} else if (curregs > availregs) {
+					/*
+					 * Race detected: the counters were read
+					 * in separate mallctl calls and
+					 * concurrent operations happened in
+					 * between. In this case no meaningful
+					 * utilization can be computed.
+					 */
+					malloc_snprintf(util, sizeof(util),
+					    " race");
+				} else {
+					not_reached();
+				}
 			}
+			char rate[6];
+			if (get_rate_str(lock_data.n_wait_times,
+			    lock_data.n_lock_ops, rate)) {
+				if (lock_data.n_lock_ops == 0) {
+					malloc_snprintf(rate, sizeof(rate),
+					    "0");
+				}
+			}
+			uint64_t max_wait = nstime_msec(
+			    &lock_data.max_wait_time);
 
 			if (config_tcache) {
 				malloc_cprintf(write_cb, cbopaque,
 				    "%20zu %3u %12zu %12"FMTu64
 				    " %12"FMTu64" %12"FMTu64" %12zu"
 				    " %12zu %4u %3zu %-5s %12"FMTu64
-				    " %12"FMTu64" %12"FMTu64" %12"FMTu64"\n",
+				    " %12"FMTu64" %12"FMTu64" %12"FMTu64
+				    " %12s %12"FMTu64"\n",
 				    reg_size, j, curregs * reg_size, nmalloc,
 				    ndalloc, nrequests, curregs, curslabs,
 				    nregs, slab_size / page, util, nfills,
-				    nflushes, nslabs, nreslabs);
+				    nflushes, nslabs, nreslabs, rate, max_wait);
 			} else {
 				malloc_cprintf(write_cb, cbopaque,
 				    "%20zu %3u %12zu %12"FMTu64
 				    " %12"FMTu64" %12"FMTu64" %12zu"
 				    " %12zu %4u %3zu %-5s %12"FMTu64
-				    " %12"FMTu64"\n",
+				    " %12"FMTu64" %12s\n",
 				    reg_size, j, curregs * reg_size, nmalloc,
 				    ndalloc, nrequests, curregs, curslabs,
 				    nregs, slab_size / page, util, nslabs,
-				    nreslabs);
+				    nreslabs, rate);
 			}
 		}
 	}