[merged] mm-micro-optimisation-save-two-branches-on-hot-page-allocation-path.patch removed from -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm, pagealloc: micro-optimisation: save two branches on hot page allocation path
has been removed from the -mm tree.  Its filename was
     mm-micro-optimisation-save-two-branches-on-hot-page-allocation-path.patch

This patch was dropped because it was merged into mainline or a subsystem tree

------------------------------------------------------
From: Mateusz Nosek <mateusznosek0@gmail.com>
Subject: mm, pagealloc: micro-optimisation: save two branches on hot page allocation path

This patch makes ALLOC_KSWAPD equal to __GFP_KSWAPD_RECLAIM (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 beginning of page allocation and the second
one in loop in page allocator slowpath.

Link: http://lkml.kernel.org/r/20200304162118.14784-1-mateusznosek0@gmail.com
Signed-off-by: Mateusz Nosek <mateusznosek0@gmail.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/internal.h   |    2 +-
 mm/page_alloc.c |   22 ++++++++++++++--------
 2 files changed, 15 insertions(+), 9 deletions(-)

--- a/mm/internal.h~mm-micro-optimisation-save-two-branches-on-hot-page-allocation-path
+++ a/mm/internal.h
@@ -555,7 +555,7 @@ unsigned long reclaim_clean_pages_from_l
 #else
 #define ALLOC_NOFRAGMENT	  0x0
 #endif
-#define ALLOC_KSWAPD		0x200 /* allow waking of kswapd */
+#define ALLOC_KSWAPD		0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
 
 enum ttu_flags;
 struct tlbflush_unmap_batch;
--- a/mm/page_alloc.c~mm-micro-optimisation-save-two-branches-on-hot-page-allocation-path
+++ a/mm/page_alloc.c
@@ -3536,10 +3536,13 @@ static bool zone_allows_reclaim(struct z
 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.
+	 */
+	alloc_flags = (__force int) (gfp_mask & __GFP_KSWAPD_RECLAIM);
 
 #ifdef CONFIG_ZONE_DMA32
 	if (!zone)
@@ -4175,8 +4178,13 @@ 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
@@ -4184,7 +4192,8 @@ 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) {
 		/*
@@ -4201,9 +4210,6 @@ 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;