Add MALLOC_CONF parsing for dynamic slab sizes.

This actually enables us to change the values.

test/integration/slab_sizes.c

@@ -0,0 +1,80 @@
+#include "test/jemalloc_test.h"
+
+/* Note that this test relies on the unusual slab sizes set in slab_sizes.sh. */
+
+TEST_BEGIN(test_slab_sizes) {
+	unsigned nbins;
+	size_t page;
+	size_t sizemib[4];
+	size_t slabmib[4];
+	size_t len;
+
+	len = sizeof(nbins);
+	assert_d_eq(mallctl("arenas.nbins", &nbins, &len, NULL, 0), 0,
+	    "nbins mallctl failure");
+
+	len = sizeof(page);
+	assert_d_eq(mallctl("arenas.page", &page, &len, NULL, 0), 0,
+	    "page mallctl failure");
+
+	len = 4;
+	assert_d_eq(mallctlnametomib("arenas.bin.0.size", sizemib, &len), 0,
+	    "bin size mallctlnametomib failure");
+
+	len = 4;
+	assert_d_eq(mallctlnametomib("arenas.bin.0.slab_size", slabmib, &len),
+	    0, "slab size mallctlnametomib failure");
+
+	size_t biggest_slab_seen = 0;
+
+	for (unsigned i = 0; i < nbins; i++) {
+		size_t bin_size;
+		size_t slab_size;
+		len = sizeof(size_t);
+		sizemib[2] = i;
+		slabmib[2] = i;
+		assert_d_eq(mallctlbymib(sizemib, 4, (void *)&bin_size, &len,
+		    NULL, 0), 0, "bin size mallctlbymib failure");
+
+		len = sizeof(size_t);
+		assert_d_eq(mallctlbymib(slabmib, 4, (void *)&slab_size, &len,
+		    NULL, 0), 0, "slab size mallctlbymib failure");
+
+		if (bin_size < 100) {
+			/*
+			 * Then we should be as close to 17 as possible.  Since
+			 * not all page sizes are valid (because of bitmap
+			 * limitations on the number of items in a slab), we
+			 * should at least make sure that the number of pages
+			 * goes up.
+			 */
+			assert_zu_ge(slab_size, biggest_slab_seen,
+			    "Slab sizes should go up");
+			biggest_slab_seen = slab_size;
+		} else if (
+		    (100 <= bin_size && bin_size < 128)
+		    || (128 < bin_size && bin_size <= 200)) {
+			assert_zu_eq(slab_size, page,
+			    "Forced-small slabs should be small");
+		} else if (bin_size == 128) {
+			assert_zu_eq(slab_size, 2 * page,
+			    "Forced-2-page slab should be 2 pages");
+		} else if (200 < bin_size && bin_size <= 4096) {
+			assert_zu_ge(slab_size, biggest_slab_seen,
+			    "Slab sizes should go up");
+			biggest_slab_seen = slab_size;
+		}
+	}
+	/*
+	 * For any reasonable configuration, 17 pages should be a valid slab
+	 * size for 4096-byte items.
+	 */
+	assert_zu_eq(biggest_slab_seen, 17 * page, "Didn't hit page target");
+}
+TEST_END
+
+int
+main(void) {
+	return test(
+	    test_slab_sizes);
+}