SC: Add page customization functionality.

Makefile.in

@@ -204,6 +204,7 @@ TESTS_UNIT := \
 	$(srcroot)test/unit/rtree.c \
 	$(srcroot)test/unit/seq.c \
 	$(srcroot)test/unit/SFMT.c \
+	$(srcroot)test/unit/sc.c \
 	$(srcroot)test/unit/size_classes.c \
 	$(srcroot)test/unit/slab.c \
 	$(srcroot)test/unit/smoothstep.c \

include/jemalloc/internal/sc.h

@@ -297,6 +297,12 @@ struct sc_data_s {
 
 extern sc_data_t sc_data_global;
 void sc_data_init(sc_data_t *data);
+/*
+ * Updates slab sizes in [begin, end] to be pgs pages in length, if possible.
+ * Otherwise, does its best to accomodate the request.
+ */
+void sc_data_update_slab_size(sc_data_t *data, size_t begin, size_t end,
+    int pgs);
 void sc_boot();
 
 #endif /* JEMALLOC_INTERNAL_SC_H */

src/sc.c

@@ -2,6 +2,8 @@
 
 #include "jemalloc/internal/assert.h"
 #include "jemalloc/internal/bit_util.h"
+#include "jemalloc/internal/bitmap.h"
+#include "jemalloc/internal/pages.h"
 #include "jemalloc/internal/sc.h"
 
 /*
@@ -240,6 +242,46 @@ sc_data_init(sc_data_t *sc_data) {
 	sc_data->initialized = true;
 }
 
+static void
+sc_data_update_sc_slab_size(sc_t *sc, size_t reg_size, size_t pgs_guess) {
+	size_t min_pgs = reg_size / PAGE;
+	if (reg_size % PAGE != 0) {
+		min_pgs++;
+	}
+	/*
+	 * BITMAP_MAXBITS is actually determined by putting the smallest
+	 * possible size-class on one page, so this can never be 0.
+	 */
+	size_t max_pgs = BITMAP_MAXBITS * reg_size / PAGE;
+
+	assert(min_pgs <= max_pgs);
+	assert(min_pgs > 0);
+	assert(max_pgs >= 1);
+	if (pgs_guess < min_pgs) {
+		sc->pgs = (int)min_pgs;
+	} else if (pgs_guess > max_pgs) {
+		sc->pgs = (int)max_pgs;
+	} else {
+		sc->pgs = (int)pgs_guess;
+	}
+}
+
+void
+sc_data_update_slab_size(sc_data_t *data, size_t begin, size_t end, int pgs) {
+	assert(data->initialized);
+	for (int i = 0; i < data->nsizes; i++) {
+		sc_t *sc = &data->sc[i];
+		if (!sc->bin) {
+			break;
+		}
+		size_t reg_size = reg_size_compute(sc->lg_base, sc->lg_delta,
+		    sc->ndelta);
+		if (begin <= reg_size && reg_size <= end) {
+			sc_data_update_sc_slab_size(sc, reg_size, pgs);
+		}
+	}
+}
+
 void
 sc_boot() {
 	sc_data_init(&sc_data_global);

test/unit/sc.c

@@ -0,0 +1,33 @@
+#include "test/jemalloc_test.h"
+
+TEST_BEGIN(test_update_slab_size) {
+	sc_data_t data;
+	memset(&data, 0, sizeof(data));
+	sc_data_init(&data);
+	sc_t *tiny = &data.sc[0];
+	size_t tiny_size = (ZU(1) << tiny->lg_base)
+	    + (ZU(tiny->ndelta) << tiny->lg_delta);
+	size_t pgs_too_big = (tiny_size * BITMAP_MAXBITS + PAGE - 1) / PAGE + 1;
+	sc_data_update_slab_size(&data, tiny_size, tiny_size, (int)pgs_too_big);
+	assert_zu_lt((size_t)tiny->pgs, pgs_too_big, "Allowed excessive pages");
+
+	sc_data_update_slab_size(&data, 1, 10 * PAGE, 1);
+	for (int i = 0; i < data.nbins; i++) {
+		sc_t *sc = &data.sc[i];
+		size_t reg_size = (ZU(1) << sc->lg_base)
+		    + (ZU(sc->ndelta) << sc->lg_delta);
+		if (reg_size <= PAGE) {
+			assert_d_eq(sc->pgs, 1, "Ignored valid page size hint");
+		} else {
+			assert_d_gt(sc->pgs, 1,
+			    "Allowed invalid page size hint");
+		}
+	}
+}
+TEST_END
+
+int
+main(void) {
+	return test(
+	    test_update_slab_size);
+}