[PATCH] mm/zsmalloc: simplify zs_max_alloc_size handling

Jerome Marchand
2017-06-28T08:14:36Z

Commit 40f9fb8cffc6 ("mm/zsmalloc: support allocating obj with size of
ZS_MAX_ALLOC_SIZE") fixes a size calculation error that prevented
zsmalloc to allocate an object of the maximal size
(ZS_MAX_ALLOC_SIZE). I think however the fix is unneededly
complicated.

This patch replaces the dynamic calculation of zs_size_classes at init
time by a compile time calculation that uses the DIV_ROUND_UP() macro
already used in get_size_class_index().

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
---
mm/zsmalloc.c | 52 +++++++++++++++-------------------------------------
1 file changed, 15 insertions(+), 37 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index d41edd2..134024b 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -116,6 +116,11 @@
#define OBJ_INDEX_BITS (BITS_PER_LONG - _PFN_BITS - OBJ_TAG_BITS)
#define OBJ_INDEX_MASK ((_AC(1, UL) << OBJ_INDEX_BITS) - 1)

+#define FULLNESS_BITS 2
+#define CLASS_BITS 8
+#define ISOLATED_BITS 3
+#define MAGIC_VAL_BITS 8
+
#define MAX(a, b) ((a) >= (b) ? (a) : (b))
/* ZS_MIN_ALLOC_SIZE must be multiple of ZS_ALIGN */
#define ZS_MIN_ALLOC_SIZE \
@@ -137,6 +142,8 @@
* (reason above)
*/
#define ZS_SIZE_CLASS_DELTA (PAGE_SIZE >> CLASS_BITS)
+#define ZS_SIZE_CLASSES DIV_ROUND_UP(ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE, \
+ ZS_SIZE_CLASS_DELTA)

enum fullness_group {
ZS_EMPTY,
@@ -169,11 +176,6 @@ static struct vfsmount *zsmalloc_mnt;
#endif

/*
- * number of size_classes
- */
-static int zs_size_classes;
-
-/*
* We assign a page to ZS_ALMOST_EMPTY fullness group when:
* n <= N / f, where
* n = number of allocated objects
@@ -244,7 +246,7 @@ struct link_free {
struct zs_pool {
const char *name;

- struct size_class **size_class;
+ struct size_class *size_class[ZS_SIZE_CLASSES];
struct kmem_cache *handle_cachep;
struct kmem_cache *zspage_cachep;

@@ -268,11 +270,6 @@ struct zs_pool {
#endif
};

-#define FULLNESS_BITS 2
-#define CLASS_BITS 8
-#define ISOLATED_BITS 3
-#define MAGIC_VAL_BITS 8
-
struct zspage {
struct {
unsigned int fullness:FULLNESS_BITS;
@@ -551,7 +548,7 @@ static int get_size_class_index(int size)
idx = DIV_ROUND_UP(size - ZS_MIN_ALLOC_SIZE,
ZS_SIZE_CLASS_DELTA);

- return min(zs_size_classes - 1, idx);
+ return min((int)ZS_SIZE_CLASSES - 1, idx);
}

static inline void zs_stat_inc(struct size_class *class,
@@ -610,7 +607,7 @@ static int zs_stats_size_show(struct seq_file *s, void *v)
"obj_allocated", "obj_used", "pages_used",
"pages_per_zspage", "freeable");

- for (i = 0; i < zs_size_classes; i++) {
+ for (i = 0; i < ZS_SIZE_CLASSES; i++) {
class = pool->size_class[i];

if (class->index != i)
@@ -1294,17 +1291,6 @@ static int zs_cpu_dead(unsigned int cpu)
return 0;
}

-static void __init init_zs_size_classes(void)
-{
- int nr;
-
- nr = (ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / ZS_SIZE_CLASS_DELTA + 1;
- if ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) % ZS_SIZE_CLASS_DELTA)
- nr += 1;
-
- zs_size_classes = nr;
-}
-
static bool can_merge(struct size_class *prev, int pages_per_zspage,
int objs_per_zspage)
{
@@ -2145,7 +2131,7 @@ static void async_free_zspage(struct work_struct *work)
struct zs_pool *pool = container_of(work, struct zs_pool,
free_work);

- for (i = 0; i < zs_size_classes; i++) {
+ for (i = 0; i < ZS_SIZE_CLASSES; i++) {
class = pool->size_class[i];
if (class->index != i)
continue;
@@ -2263,7 +2249,7 @@ unsigned long zs_compact(struct zs_pool *pool)
int i;
struct size_class *class;

- for (i = zs_size_classes - 1; i >= 0; i--) {
+ for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
class = pool->size_class[i];
if (!class)
continue;
@@ -2309,7 +2295,7 @@ static unsigned long zs_shrinker_count(struct shrinker *shrinker,
struct zs_pool *pool = container_of(shrinker, struct zs_pool,
shrinker);

- for (i = zs_size_classes - 1; i >= 0; i--) {
+ for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
class = pool->size_class[i];
if (!class)
continue;
@@ -2361,12 +2347,6 @@ struct zs_pool *zs_create_pool(const char *name)
return NULL;

init_deferred_free(pool);
- pool->size_class = kcalloc(zs_size_classes, sizeof(struct size_class *),
- GFP_KERNEL);
- if (!pool->size_class) {
- kfree(pool);
- return NULL;
- }

pool->name = kstrdup(name, GFP_KERNEL);
if (!pool->name)
@@ -2379,7 +2359,7 @@ struct zs_pool *zs_create_pool(const char *name)
* Iterate reversely, because, size of size_class that we want to use
* for merging should be larger or equal to current size.
*/
- for (i = zs_size_classes - 1; i >= 0; i--) {
+ for (i = ZS_SIZE_CLASSES - 1; i >= 0; i--) {
int size;
int pages_per_zspage;
int objs_per_zspage;
@@ -2453,7 +2433,7 @@ void zs_destroy_pool(struct zs_pool *pool)
zs_unregister_migration(pool);
zs_pool_stat_destroy(pool);

- for (i = 0; i < zs_size_classes; i++) {
+ for (i = 0; i < ZS_SIZE_CLASSES; i++) {
int fg;
struct size_class *class = pool->size_class[i];

@@ -2492,8 +2472,6 @@ static int __init zs_init(void)
if (ret)
goto hp_setup_fail;

- init_zs_size_classes();
-
#ifdef CONFIG_ZPOOL
zpool_register_driver(&zs_zpool_driver);
#endif
--
2.9.4