Jemalloc updated to 3.6.0.

Not a single bug in about 3 months, and our previous version was
too old (3.2.0).

deps/jemalloc/test/unit/prof_accum.c

@@ -0,0 +1,86 @@
+#include "prof_accum.h"
+
+#ifdef JEMALLOC_PROF
+const char *malloc_conf =
+    "prof:true,prof_accum:true,prof_active:false,lg_prof_sample:0";
+#endif
+
+static int
+prof_dump_open_intercept(bool propagate_err, const char *filename)
+{
+	int fd;
+
+	fd = open("/dev/null", O_WRONLY);
+	assert_d_ne(fd, -1, "Unexpected open() failure");
+
+	return (fd);
+}
+
+static void *
+alloc_from_permuted_backtrace(unsigned thd_ind, unsigned iteration)
+{
+
+	return (alloc_0(thd_ind*NALLOCS_PER_THREAD + iteration));
+}
+
+static void *
+thd_start(void *varg)
+{
+	unsigned thd_ind = *(unsigned *)varg;
+	size_t bt_count_prev, bt_count;
+	unsigned i_prev, i;
+
+	i_prev = 0;
+	bt_count_prev = 0;
+	for (i = 0; i < NALLOCS_PER_THREAD; i++) {
+		void *p = alloc_from_permuted_backtrace(thd_ind, i);
+		dallocx(p, 0);
+		if (i % DUMP_INTERVAL == 0) {
+			assert_d_eq(mallctl("prof.dump", NULL, NULL, NULL, 0),
+			    0, "Unexpected error while dumping heap profile");
+		}
+
+		if (i % BT_COUNT_CHECK_INTERVAL == 0 ||
+		    i+1 == NALLOCS_PER_THREAD) {
+			bt_count = prof_bt_count();
+			assert_zu_le(bt_count_prev+(i-i_prev), bt_count,
+			    "Expected larger backtrace count increase");
+			i_prev = i;
+			bt_count_prev = bt_count;
+		}
+	}
+
+	return (NULL);
+}
+
+TEST_BEGIN(test_idump)
+{
+	bool active;
+	thd_t thds[NTHREADS];
+	unsigned thd_args[NTHREADS];
+	unsigned i;
+
+	test_skip_if(!config_prof);
+
+	active = true;
+	assert_d_eq(mallctl("prof.active", NULL, NULL, &active, sizeof(active)),
+	    0, "Unexpected mallctl failure while activating profiling");
+
+	prof_dump_open = prof_dump_open_intercept;
+
+	for (i = 0; i < NTHREADS; i++) {
+		thd_args[i] = i;
+		thd_create(&thds[i], thd_start, (void *)&thd_args[i]);
+	}
+	for (i = 0; i < NTHREADS; i++)
+		thd_join(thds[i], NULL);
+}
+TEST_END
+
+int
+main(void)
+{
+
+	return (test(
+	    test_idump));
+}