[PATCH v3] mm/zsmalloc: avoid duplicate assignment of prev_class

From: Ganesh Mahendran
Date: Tue Nov 25 2014 - 08:01:07 EST


In zs_create_pool(), prev_class is assigned (ZS_SIZE_CLASSES - 1)
times. And the prev_class only references to the previous size_class.
So we do not need unnecessary assignement.

This patch assigns *prev_class* when a new size_class structure
is allocated and uses prev_class to check whether the first class
has been allocated.

Signed-off-by: Ganesh Mahendran <opensource.ganesh@xxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Nitin Gupta <ngupta@xxxxxxxxxx>
Cc: Dan Streetman <ddstreet@xxxxxxxx>

---
v1 -> v2:
- follow Dan Streetman's advise to use prev_class to
check whether the first class has been allocated
- follow Minchan Kim's advise to remove uninitialized_var()

v2 -> v3:
- move *prev_class* definition out of the loop - Dan
---
mm/zsmalloc.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index 83ecdb6..de1320e 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -966,6 +966,7 @@ struct zs_pool *zs_create_pool(gfp_t flags)
{
int i, ovhd_size;
struct zs_pool *pool;
+ struct size_class *prev_class = NULL;

ovhd_size = roundup(sizeof(*pool), PAGE_SIZE);
pool = kzalloc(ovhd_size, GFP_KERNEL);
@@ -980,7 +981,6 @@ struct zs_pool *zs_create_pool(gfp_t flags)
int size;
int pages_per_zspage;
struct size_class *class;
- struct size_class *prev_class;

size = ZS_MIN_ALLOC_SIZE + i * ZS_SIZE_CLASS_DELTA;
if (size > ZS_MAX_ALLOC_SIZE)
@@ -996,8 +996,7 @@ struct zs_pool *zs_create_pool(gfp_t flags)
* characteristics. So, we makes size_class point to
* previous size_class if possible.
*/
- if (i < ZS_SIZE_CLASSES - 1) {
- prev_class = pool->size_class[i + 1];
+ if (prev_class) {
if (can_merge(prev_class, size, pages_per_zspage)) {
pool->size_class[i] = prev_class;
continue;
@@ -1013,6 +1012,8 @@ struct zs_pool *zs_create_pool(gfp_t flags)
class->pages_per_zspage = pages_per_zspage;
spin_lock_init(&class->lock);
pool->size_class[i] = class;
+
+ prev_class = class;
}

pool->flags = flags;
--
1.7.9.5

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