Add a benchmark of large allocations.

test/stress/large_microbench.c

@@ -0,0 +1,33 @@
+#include "test/jemalloc_test.h"
+#include "test/bench.h"
+
+static void
+large_mallocx_free(void) {
+	/*
+	 * We go a bit larger than the large minclass on its own to better
+	 * expose costs from things like zeroing.
+	 */
+	void *p = mallocx(SC_LARGE_MINCLASS, MALLOCX_TCACHE_NONE);
+	assert_ptr_not_null(p, "mallocx shouldn't fail");
+	free(p);
+}
+
+static void
+small_mallocx_free(void) {
+	void *p = mallocx(16, 0);
+	assert_ptr_not_null(p, "mallocx shouldn't fail");
+	free(p);
+}
+
+TEST_BEGIN(test_large_vs_small) {
+	compare_funcs(100*1000, 1*1000*1000, "large mallocx",
+	    large_mallocx_free, "small mallocx", small_mallocx_free);
+}
+TEST_END
+
+int
+main(void) {
+	return test_no_reentrancy(
+	    test_large_vs_small);
+}
+