diff --git a/include/jemalloc/internal/activity_callback.h b/include/jemalloc/internal/activity_callback.h
new file mode 100644
index 00000000..6c2e84e3
--- /dev/null
+++ b/include/jemalloc/internal/activity_callback.h
@@ -0,0 +1,23 @@
+#ifndef JEMALLOC_INTERNAL_ACTIVITY_CALLBACK_H
+#define JEMALLOC_INTERNAL_ACTIVITY_CALLBACK_H
+
+/*
+ * The callback to be executed "periodically", in response to some amount of
+ * allocator activity.
+ *
+ * This callback need not be computing any sort of peak (although that's the
+ * intended first use case), but we drive it from the peak counter, so it's
+ * keeps things tidy to keep it here.
+ *
+ * The calls to this thunk get driven by the peak_event module.
+ */
+#define ACTIVITY_CALLBACK_THUNK_INITIALIZER {NULL, NULL}
+typedef void (*activity_callback_t)(void *uctx, uint64_t allocated,
+    uint64_t deallocated);
+typedef struct activity_callback_thunk_s activity_callback_thunk_t;
+struct activity_callback_thunk_s {
+	activity_callback_t callback;
+	void *uctx;
+};
+
+#endif /* JEMALLOC_INTERNAL_ACTIVITY_CALLBACK_H */
diff --git a/include/jemalloc/internal/tsd.h b/include/jemalloc/internal/tsd.h
index 5ac85e14..60764199 100644
--- a/include/jemalloc/internal/tsd.h
+++ b/include/jemalloc/internal/tsd.h
@@ -1,6 +1,7 @@
 #ifndef JEMALLOC_INTERNAL_TSD_H
 #define JEMALLOC_INTERNAL_TSD_H
 
+#include "jemalloc/internal/activity_callback.h"
 #include "jemalloc/internal/arena_types.h"
 #include "jemalloc/internal/assert.h"
 #include "jemalloc/internal/bin_types.h"
@@ -82,6 +83,8 @@ typedef ql_elm(tsd_t) tsd_link_t;
     O(tsd_link,			tsd_link_t,		tsd_link_t)	\
     O(in_hook,			bool,			bool)		\
     O(peak,			peak_t,			peak_t)		\
+    O(activity_callback_thunk,	activity_callback_thunk_t,		\
+	activity_callback_thunk_t)					\
     O(tcache_slow,		tcache_slow_t,		tcache_slow_t)	\
     O(rtree_ctx,		rtree_ctx_t,		rtree_ctx_t)
 
@@ -112,6 +115,8 @@ typedef ql_elm(tsd_t) tsd_link_t;
     /* tsd_link */		{NULL},					\
     /* in_hook */		false,					\
     /* peak */			PEAK_INITIALIZER,			\
+    /* activity_callback_thunk */					\
+	ACTIVITY_CALLBACK_THUNK_INITIALIZER,				\
     /* tcache_slow */		TCACHE_SLOW_ZERO_INITIALIZER,		\
     /* rtree_ctx */		RTREE_CTX_ZERO_INITIALIZER,
 
diff --git a/src/ctl.c b/src/ctl.c
index 874aaac2..d5dd1d16 100644
--- a/src/ctl.c
+++ b/src/ctl.c
@@ -264,6 +264,7 @@ CTL_PROTO(stats_retained)
 CTL_PROTO(stats_zero_reallocs)
 CTL_PROTO(experimental_hooks_install)
 CTL_PROTO(experimental_hooks_remove)
+CTL_PROTO(experimental_thread_activity_callback)
 CTL_PROTO(experimental_utilization_query)
 CTL_PROTO(experimental_utilization_batch_query)
 CTL_PROTO(experimental_arenas_i_pactivep)
@@ -712,6 +713,11 @@ static const ctl_named_node_t experimental_hooks_node[] = {
 	{NAME("remove"),	CTL(experimental_hooks_remove)}
 };
 
+static const ctl_named_node_t experimental_thread_node[] = {
+	{NAME("activity_callback"),
+		CTL(experimental_thread_activity_callback)}
+};
+
 static const ctl_named_node_t experimental_utilization_node[] = {
 	{NAME("query"),		CTL(experimental_utilization_query)},
 	{NAME("batch_query"),	CTL(experimental_utilization_batch_query)}
@@ -738,7 +744,8 @@ static const ctl_named_node_t experimental_node[] = {
 	{NAME("utilization"),	CHILD(named, experimental_utilization)},
 	{NAME("arenas"),	CHILD(indexed, experimental_arenas)},
 	{NAME("prof_recent"),	CHILD(named, experimental_prof_recent)},
-	{NAME("batch_alloc"),	CTL(experimental_batch_alloc)}
+	{NAME("batch_alloc"),	CTL(experimental_batch_alloc)},
+	{NAME("thread"),	CHILD(named, experimental_thread)}
 };
 
 static const ctl_named_node_t	root_node[] = {
@@ -3428,6 +3435,32 @@ label_return:
 	return ret;
 }
 
+static int
+experimental_thread_activity_callback_ctl(tsd_t *tsd, const size_t *mib,
+    size_t miblen, void *oldp, size_t *oldlenp, void *newp, size_t newlen) {
+	int ret;
+
+	if (!config_stats) {
+		return ENOENT;
+	}
+
+	activity_callback_thunk_t t_old = tsd_activity_callback_thunk_get(tsd);
+	READ(t_old, activity_callback_thunk_t);
+
+	if (newp != NULL) {
+		/*
+		 * This initialization is unnecessary.  If it's omitted, though,
+		 * clang gets confused and warns on the subsequent use of t_new.
+		 */
+		activity_callback_thunk_t t_new = {NULL, NULL};
+		WRITE(t_new, activity_callback_thunk_t);
+		tsd_activity_callback_thunk_set(tsd, t_new);
+	}
+	ret = 0;
+label_return:
+	return ret;
+}
+
 /*
  * Output six memory utilization entries for an input pointer, the first one of
  * type (void *) and the remaining five of type size_t, describing the following
diff --git a/src/peak_event.c b/src/peak_event.c
index 79d91e02..4093fbcc 100644
--- a/src/peak_event.c
+++ b/src/peak_event.c
@@ -1,9 +1,11 @@
 #include "jemalloc/internal/jemalloc_preamble.h"
 #include "jemalloc/internal/jemalloc_internal_includes.h"
 
-#include "jemalloc/internal/peak.h"
 #include "jemalloc/internal/peak_event.h"
 
+#include "jemalloc/internal/activity_callback.h"
+#include "jemalloc/internal/peak.h"
+
 /*
  * Update every 64K by default.  We're not exposing this as a configuration
  * option for now; we don't want to bind ourselves too tightly to any particular
@@ -21,6 +23,17 @@ peak_event_update(tsd_t *tsd) {
 	peak_update(peak, alloc, dalloc);
 }
 
+static void
+peak_event_activity_callback(tsd_t *tsd) {
+	activity_callback_thunk_t *thunk = tsd_activity_callback_thunkp_get(
+	    tsd);
+	uint64_t alloc = tsd_thread_allocated_get(tsd);
+	uint64_t dalloc = tsd_thread_deallocated_get(tsd);
+	if (thunk->callback != NULL) {
+		thunk->callback(thunk->uctx, alloc, dalloc);
+	}
+}
+
 /* Set current state to zero. */
 void
 peak_event_zero(tsd_t *tsd) {
@@ -49,6 +62,7 @@ peak_alloc_postponed_event_wait(tsd_t *tsd) {
 void
 peak_alloc_event_handler(tsd_t *tsd, uint64_t elapsed) {
 	peak_event_update(tsd);
+	peak_event_activity_callback(tsd);
 }
 
 uint64_t
@@ -64,4 +78,5 @@ peak_dalloc_postponed_event_wait(tsd_t *tsd) {
 void
 peak_dalloc_event_handler(tsd_t *tsd, uint64_t elapsed) {
 	peak_event_update(tsd);
+	peak_event_activity_callback(tsd);
 }
diff --git a/test/unit/mallctl.c b/test/unit/mallctl.c
index 278bd09d..d4e2621e 100644
--- a/test/unit/mallctl.c
+++ b/test/unit/mallctl.c
@@ -1030,6 +1030,77 @@ TEST_BEGIN(test_thread_peak) {
 }
 TEST_END
 
+typedef struct activity_test_data_s activity_test_data_t;
+struct activity_test_data_s {
+	uint64_t obtained_alloc;
+	uint64_t obtained_dalloc;
+};
+
+static void
+activity_test_callback(void *uctx, uint64_t alloc, uint64_t dalloc) {
+	activity_test_data_t *test_data = (activity_test_data_t *)uctx;
+	test_data->obtained_alloc = alloc;
+	test_data->obtained_dalloc = dalloc;
+}
+
+TEST_BEGIN(test_thread_activity_callback) {
+	test_skip_if(!config_stats);
+
+	const size_t big_size = 10 * 1024 * 1024;
+	void *ptr;
+	int err;
+	size_t sz;
+
+	uint64_t *allocatedp;
+	uint64_t *deallocatedp;
+	sz = sizeof(allocatedp);
+	err = mallctl("thread.allocatedp", &allocatedp, &sz, NULL, 0);
+	assert_d_eq(0, err, "");
+	err = mallctl("thread.deallocatedp", &deallocatedp, &sz, NULL, 0);
+	assert_d_eq(0, err, "");
+
+	activity_callback_thunk_t old_thunk = {(activity_callback_t)111,
+		(void *)222};
+
+	activity_test_data_t test_data = {333, 444};
+	activity_callback_thunk_t new_thunk =
+	    {&activity_test_callback, &test_data};
+
+	sz = sizeof(old_thunk);
+	err = mallctl("experimental.thread.activity_callback", &old_thunk, &sz,
+	    &new_thunk, sizeof(new_thunk));
+	assert_d_eq(0, err, "");
+
+	expect_true(old_thunk.callback == NULL, "Callback already installed");
+	expect_true(old_thunk.uctx == NULL, "Callback data already installed");
+
+	ptr = mallocx(big_size, 0);
+	expect_u64_eq(test_data.obtained_alloc, *allocatedp, "");
+	expect_u64_eq(test_data.obtained_dalloc, *deallocatedp, "");
+
+	free(ptr);
+	expect_u64_eq(test_data.obtained_alloc, *allocatedp, "");
+	expect_u64_eq(test_data.obtained_dalloc, *deallocatedp, "");
+
+	sz = sizeof(old_thunk);
+	new_thunk = (activity_callback_thunk_t){ NULL, NULL };
+	err = mallctl("experimental.thread.activity_callback", &old_thunk, &sz,
+	    &new_thunk, sizeof(new_thunk));
+	assert_d_eq(0, err, "");
+
+	expect_true(old_thunk.callback == &activity_test_callback, "");
+	expect_true(old_thunk.uctx == &test_data, "");
+
+	/* Inserting NULL should have turned off tracking. */
+	test_data.obtained_alloc = 333;
+	test_data.obtained_dalloc = 444;
+	ptr = mallocx(big_size, 0);
+	free(ptr);
+	expect_u64_eq(333, test_data.obtained_alloc, "");
+	expect_u64_eq(444, test_data.obtained_dalloc, "");
+}
+TEST_END
+
 int
 main(void) {
 	return test(
@@ -1063,5 +1134,6 @@ main(void) {
 	    test_hooks,
 	    test_hooks_exhaustion,
 	    test_thread_idle,
-	    test_thread_peak);
+	    test_thread_peak,
+	    test_thread_activity_callback);
 }