Add MALLOC_CONF parsing for dynamic slab sizes.

This actually enables us to change the values.

Makefile.in

@@ -230,6 +230,7 @@ TESTS_INTEGRATION := $(srcroot)test/integration/aligned_alloc.c \
 	$(srcroot)test/integration/posix_memalign.c \
 	$(srcroot)test/integration/rallocx.c \
 	$(srcroot)test/integration/sdallocx.c \
+	$(srcroot)test/integration/slab_sizes.c \
 	$(srcroot)test/integration/thread_arena.c \
 	$(srcroot)test/integration/thread_tcache_enabled.c \
 	$(srcroot)test/integration/xallocx.c

src/jemalloc.c

@@ -764,6 +764,49 @@ init_opt_stats_print_opts(const char *v, size_t vlen) {
 	assert(opts_len == strlen(opt_stats_print_opts));
 }
 
+static bool
+malloc_conf_slab_sizes_next(const char **slab_size_segment_cur,
+    size_t *vlen_left, size_t *slab_start, size_t *slab_end, size_t *pgs) {
+	const char *cur = *slab_size_segment_cur;
+	char *end;
+	uintmax_t um;
+
+	set_errno(0);
+
+	/* First number, then '-' */
+	um = malloc_strtoumax(cur, &end, 0);
+	if (get_errno() != 0 || *end != '-') {
+		return true;
+	}
+	*slab_start = (size_t)um;
+	cur = end + 1;
+
+	/* Second number, then ':' */
+	um = malloc_strtoumax(cur, &end, 0);
+	if (get_errno() != 0 || *end != ':') {
+		return true;
+	}
+	*slab_end = (size_t)um;
+	cur = end + 1;
+
+	/* Last number */
+	um = malloc_strtoumax(cur, &end, 0);
+	if (get_errno() != 0) {
+		return true;
+	}
+	*pgs = (size_t)um;
+
+	/* Consume the separator if there is one. */
+	if (*end == '|') {
+		end++;
+	}
+
+	*vlen_left -= end - *slab_size_segment_cur;
+	*slab_size_segment_cur = end;
+
+	return false;
+}
+
 static bool
 malloc_conf_next(char const **opts_p, char const **k_p, size_t *klen_p,
     char const **v_p, size_t *vlen_p) {
@@ -1192,6 +1235,31 @@ malloc_conf_init(void) {
 					   "max_background_threads", 1,
 					   opt_max_background_threads, yes, yes,
 					   true);
+			if (CONF_MATCH("slab_sizes")) {
+				bool err;
+				const char *slab_size_segment_cur = v;
+				size_t vlen_left = vlen;
+				do {
+					size_t slab_start;
+					size_t slab_end;
+					size_t pgs;
+					err = malloc_conf_slab_sizes_next(
+					    &slab_size_segment_cur,
+					    &vlen_left, &slab_start, &slab_end,
+					    &pgs);
+					if (!err) {
+						sc_data_update_slab_size(
+						    &sc_data_global, slab_start,
+						    slab_end, (int)pgs);
+					} else {
+						malloc_conf_error(
+						    "Invalid settings for "
+						    "slab_sizes", k, klen, v,
+						    vlen);
+					}
+				} while (!err && vlen_left > 0);
+				continue;
+			}
 			if (config_prof) {
 				CONF_HANDLE_BOOL(opt_prof, "prof")
 				CONF_HANDLE_CHAR_P(opt_prof_prefix,

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);
+}

test/integration/slab_sizes.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+# Some screwy-looking slab sizes.
+export MALLOC_CONF="slab_sizes:1-4096:17|100-200:1|128-128:2"