I sent a patch [1] for unnecessary check in zsmalloc. And Minchan Kim
found zsmalloc even does not support allocating an obj with the size of
ZS_MAX_ALLOC_SIZE in some situations.
For example:
In system with 64KB PAGE_SIZE and 32 bit of physical addr. Then:
ZS_MIN_ALLOC_SIZE is 32 bytes which is calculated by:
MAX(32, (ZS_MAX_PAGES_PER_ZSPAGE << PAGE_SHIFT >> OBJ_INDEX_BITS))
ZS_MAX_ALLOC_SIZE is 64KB(in current code, is PAGE_SIZE)
ZS_SIZE_CLASS_DELTA is 256 bytes
So, ZS_SIZE_CLASSES = (ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) /
ZS_SIZE_CLASS_DELTA + 1
= 256
In zs_create_pool(), the max size obj which can be allocated will be:
ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA = 32 + 255*256 = 65312
We can see that 65312 < 65536 (ZS_MAX_ALLOC_SIZE). So we can NOT
allocate objs with size ZS_MAX_ALLOC_SIZE(65536) which we promise upper
users we can do.
[1] http://lkml.iu.edu/hypermail/linux/kernel/1411.2/03835.html
[2] http://lkml.iu.edu/hypermail/linux/kernel/1411.2/04534.html
This patch fix this issue by dynamiclly calculating zs_size_classes when
module is loaded, allocates buffer with size ZS_MAX_ALLOC_SIZE. Then
the max obj(size is ZS_MAX_ALLOC_SIZE) can be stored in it.
Signed-off-by: Mahendran Ganesh <[email protected]>
Suggested-by: Minchan Kim <[email protected]>
---
mm/zsmalloc.c | 40 ++++++++++++++++++++++++++++++++--------
1 file changed, 32 insertions(+), 8 deletions(-)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 480fa4c..a79889b 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -155,8 +155,6 @@
* (reason above)
*/
#define ZS_SIZE_CLASS_DELTA (PAGE_SIZE >> 8)
-#define ZS_SIZE_CLASSES ((ZS_MAX_ALLOC_SIZE - ZS_MIN_ALLOC_SIZE) / \
- ZS_SIZE_CLASS_DELTA + 1)
/*
* We do not maintain any list for completely empty or full pages
@@ -171,6 +169,11 @@ enum fullness_group {
};
/*
+ * 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
@@ -214,7 +217,7 @@ struct link_free {
};
struct zs_pool {
- struct size_class *size_class[ZS_SIZE_CLASSES];
+ struct size_class **size_class;
gfp_t flags; /* allocation flags used when growing pool */
atomic_long_t pages_allocated;
@@ -785,7 +788,7 @@ static inline int __zs_cpu_up(struct mapping_area *area)
*/
if (area->vm_buf)
return 0;
- area->vm_buf = (char *)__get_free_page(GFP_KERNEL);
+ area->vm_buf = kmalloc(ZS_MAX_ALLOC_SIZE, GFP_KERNEL);
if (!area->vm_buf)
return -ENOMEM;
return 0;
@@ -793,8 +796,7 @@ static inline int __zs_cpu_up(struct mapping_area *area)
static inline void __zs_cpu_down(struct mapping_area *area)
{
- if (area->vm_buf)
- free_page((unsigned long)area->vm_buf);
+ kfree(area->vm_buf);
area->vm_buf = NULL;
}
@@ -912,6 +914,17 @@ static int zs_register_cpu_notifier(void)
return notifier_to_errno(ret);
}
+static void 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 void __exit zs_exit(void)
{
#ifdef CONFIG_ZPOOL
@@ -929,6 +942,8 @@ static int __init zs_init(void)
return ret;
}
+ init_zs_size_classes();
+
#ifdef CONFIG_ZPOOL
zpool_register_driver(&zs_zpool_driver);
#endif
@@ -972,11 +987,18 @@ struct zs_pool *zs_create_pool(gfp_t flags)
if (!pool)
return NULL;
+ pool->size_class = kcalloc(zs_size_classes, sizeof(struct size_class *),
+ GFP_KERNEL);
+ if (!pool->size_class) {
+ kfree(pool);
+ return NULL;
+ }
+
/*
* Iterate reversly, 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;
struct size_class *class;
@@ -1030,7 +1052,7 @@ void zs_destroy_pool(struct zs_pool *pool)
{
int i;
- 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];
@@ -1048,6 +1070,8 @@ void zs_destroy_pool(struct zs_pool *pool)
}
kfree(class);
}
+
+ kfree(pool->size_class);
kfree(pool);
}
EXPORT_SYMBOL_GPL(zs_destroy_pool);
--
1.7.9.5