From: Mateusz Nosek <mateusznosek0@xxxxxxxxx>
This patch makes ALLOC_KSWAPD
equal to __GFP_KSWAPD_RACLAIM (cast to 'int').
Thanks to that code like:
```if (gfp_mask & __GFP_KSWAPD_RECLAIM)
alloc_flags |= ALLOC_KSWAPD;```
can be changed to:
```alloc_flags |= (__force int) (gfp_mask &__GFP_KSWAPD_RECLAIM);```
Thanks to this one branch less is generated in the assembly.
In case of ALLOC_KSWAPD flag two branches are saved,
first one in code that always executes in the beggining of page allocation
and the second one in loop in page allocator slowpath.
Signed-off-by: Mateusz Nosek <mateusznosek0@xxxxxxxxx>
---
mm/internal.h | 2 +-
mm/page_alloc.c | 23 +++++++++++++++--------
2 files changed, 16 insertions(+), 9 deletions(-)
diff --git a/mm/internal.h b/mm/internal.h
index 86372d164476..7fb724977743 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -535,7 +535,7 @@ unsigned long reclaim_clean_pages_from_list(struct zone *zone,
#else
#define ALLOC_NOFRAGMENT 0x0
#endif
-#define ALLOC_KSWAPD 0x200 /* allow waking of kswapd */
+#define ALLOC_KSWAPD 0x800 /* allow waking of kswapd */
enum ttu_flags;
struct tlbflush_unmap_batch;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 79e950d76ffc..73afd883eab5 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3609,10 +3609,14 @@ static bool zone_allows_reclaim(struct zone *local_zone, struct zone *zone)
static inline unsigned int
alloc_flags_nofragment(struct zone *zone, gfp_t gfp_mask)
{
- unsigned int alloc_flags = 0;
+ unsigned int alloc_flags;
- if (gfp_mask & __GFP_KSWAPD_RECLAIM)
- alloc_flags |= ALLOC_KSWAPD;
+ /*
+ * __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
+ * to save a branch.
+ */
+ BUILD_BUG_ON(__GFP_KSWAPD_RECLAIM != (__force gfp_t) ALLOC_KSWAPD);
+ alloc_flags = (__force int) (gfp_mask & __GFP_KSWAPD_RECLAIM);
#ifdef CONFIG_ZONE_DMA32
if (!zone)
@@ -4248,8 +4252,13 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
{
unsigned int alloc_flags = ALLOC_WMARK_MIN | ALLOC_CPUSET;
- /* __GFP_HIGH is assumed to be the same as ALLOC_HIGH to save a branch. */
+ /*
+ * __GFP_HIGH is assumed to be the same as ALLOC_HIGH
+ * and __GFP_KSWAPD_RECLAIM is assumed to be the same as ALLOC_KSWAPD
+ * to save two branches.
+ */
BUILD_BUG_ON(__GFP_HIGH != (__force gfp_t) ALLOC_HIGH);
+ BUILD_BUG_ON(__GFP_KSWAPD_RECLAIM != (__force gfp_t) ALLOC_KSWAPD);
/*
* The caller may dip into page reserves a bit more if the caller
@@ -4257,7 +4266,8 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
* policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will
* set both ALLOC_HARDER (__GFP_ATOMIC) and ALLOC_HIGH (__GFP_HIGH).
*/
- alloc_flags |= (__force int) (gfp_mask & __GFP_HIGH);
+ alloc_flags |= (__force int)
+ (gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));
if (gfp_mask & __GFP_ATOMIC) {
/*
@@ -4274,9 +4284,6 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
} else if (unlikely(rt_task(current)) && !in_interrupt())
alloc_flags |= ALLOC_HARDER;
- if (gfp_mask & __GFP_KSWAPD_RECLAIM)
- alloc_flags |= ALLOC_KSWAPD;
-
#ifdef CONFIG_CMA
if (gfpflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE)
alloc_flags |= ALLOC_CMA;
--
2.17.1
