[PATCH] mm/compaction: remove unnecessary order check in try_to_compact_pages()

[PATCH] mm/compaction: remove unnecessary order check in try_to_compact_pages()

[Ganesh Mahendran]

The caller __alloc_pages_direct_compact() already check (order == 0).
So no need to check again.

Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.com>
---
 mm/compaction.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index fbb7b38..500acda 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1687,7 +1687,7 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order,
 	*contended = COMPACT_CONTENDED_NONE;
 
 	/* Check if the GFP flags allow compaction */
-	if (!order || !may_enter_fs || !may_perform_io)
+	if (!may_enter_fs || !may_perform_io)
 		return COMPACT_SKIPPED;
 
 	trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode);
-- 
1.9.1

Re: [PATCH] mm/compaction: remove unnecessary order check in try_to_compact_pages()

[Anshuman Khandual]

On 06/15/2016 12:22 PM, Ganesh Mahendran wrote:
> The caller __alloc_pages_direct_compact() already check (order == 0).
> So no need to check again.

Yeah, the caller (__alloc_pages_direct_compact) checks if the order of
allocation is 0. But we can remove it there and keep it in here as this
is the actual entry point for direct page compaction.

Re: [PATCH] mm/compaction: remove unnecessary order check in try_to_compact_pages()

[Andrew Morton]

On Wed, 15 Jun 2016 14:16:20 +0530 Anshuman Khandual <khandual@linux.vnet.ibm.com> wrote:

> On 06/15/2016 12:22 PM, Ganesh Mahendran wrote:
> > The caller __alloc_pages_direct_compact() already check (order == 0).
> > So no need to check again.
> 
> Yeah, the caller (__alloc_pages_direct_compact) checks if the order of
> allocation is 0. But we can remove it there and keep it in here as this
> is the actual entry point for direct page compaction.

I think the check in __alloc_pages_direct_compact() is OK - it's a bit
silly to do a (small) bunch of additional work in
__alloc_pages_direct_compact() when orer==0.