[PATCH v2 10/10] mm, cma: use spinlock instead of mutex

Joonsoo Kim
2014-06-12T03:20:10Z

Currently, we should take the mutex for manipulating bitmap.
This job may be really simple and short so we don't need to sleep
if contended. So I change it to spinlock.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

diff --git a/mm/cma.c b/mm/cma.c
index 22a5b23..3085e8c 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -27,6 +27,7 @@
#include <linux/memblock.h>
#include <linux/err.h>
#include <linux/mm.h>
+#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/sizes.h>
#include <linux/slab.h>
@@ -36,7 +37,7 @@ struct cma {
unsigned long count;
unsigned long *bitmap;
int order_per_bit; /* Order of pages represented by one bit */
- struct mutex lock;
+ spinlock_t lock;
};

/*
@@ -72,9 +73,9 @@ static void clear_cma_bitmap(struct cma *cma, unsigned long pfn, int count)
bitmapno = (pfn - cma->base_pfn) >> cma->order_per_bit;
nr_bits = cma_bitmap_pages_to_bits(cma, count);

- mutex_lock(&cma->lock);
+ spin_lock(&cma->lock);
bitmap_clear(cma->bitmap, bitmapno, nr_bits);
- mutex_unlock(&cma->lock);
+ spin_unlock(&cma->lock);
}

static int __init cma_activate_area(struct cma *cma)
@@ -112,7 +113,7 @@ static int __init cma_activate_area(struct cma *cma)
init_cma_reserved_pageblock(pfn_to_page(base_pfn));
} while (--i);

- mutex_init(&cma->lock);
+ spin_lock_init(&cma->lock);
return 0;

err:
@@ -261,11 +262,11 @@ struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
nr_bits = cma_bitmap_pages_to_bits(cma, count);

for (;;) {
- mutex_lock(&cma->lock);
+ spin_lock(&cma->lock);
bitmapno = bitmap_find_next_zero_area(cma->bitmap,
bitmap_maxno, start, nr_bits, mask);
if (bitmapno >= bitmap_maxno) {
- mutex_unlock(&cma->lock);
+ spin_unlock(&cma->lock);
break;
}
bitmap_set(cma->bitmap, bitmapno, nr_bits);
@@ -274,7 +275,7 @@ struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
* our exclusive use. If the migration fails we will take the
* lock again and unmark it.
*/
- mutex_unlock(&cma->lock);
+ spin_unlock(&cma->lock);

pfn = cma->base_pfn + (bitmapno << cma->order_per_bit);
mutex_lock(&cma_mutex);
--
1.7.9.5