mm: create a separate slab for page->ptl allocation

If DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC are enabled spinlock_t on x86_64
is 72 bytes.  For page->ptl they will be allocated from kmalloc-96 slab,
so we loose 24 on each.  An average system can easily allocate few tens
thousands of page->ptl and overhead is significant.

Let's create a separate slab for page->ptl allocation to solve this.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/init/main.c b/init/main.c
index 6ad1a533a8c7..5f191133376f 100644
--- a/init/main.c
+++ b/init/main.c
@@ -473,7 +473,7 @@ static void __init mm_init(void)
         mem_init();
         kmem_cache_init();
         percpu_init_late();
-        pgtable_cache_init();
+        pgtable_init();
         vmalloc_init();
 }