[patch 1/4] mm: memcontrol: reduce reclaim invocations for higher order requests

[Johannes Weiner]

Instead of passing the request size to direct reclaim, memcg just
manually loops around reclaiming SWAP_CLUSTER_MAX pages until the
charge can succeed.  That potentially wastes scan progress when huge
page allocations require multiple invocations, which always have to
restart from the default scan priority.

Pass the request size as a reclaim target to direct reclaim and leave
it to that code to reach the goal.

Charging will still have to loop in case concurrent allocations steal
reclaim effort, but at least it doesn't have to loop to meet even the
basic request size.  This also prepares the memcg reclaim API for use
with the planned high limit, to reclaim excess with a single call.

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
 include/linux/swap.h |  3 ++-
 mm/memcontrol.c      | 15 +++++++++------
 mm/vmscan.c          |  3 ++-
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 1b72060f093a..473a3ae4cdd6 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -327,7 +327,8 @@ extern void lru_cache_add_active_or_unevictable(struct page *page,
 extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 					gfp_t gfp_mask, nodemask_t *mask);
 extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
-extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
+extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
+						  unsigned long nr_pages,
 						  gfp_t gfp_mask, bool noswap);
 extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
 						gfp_t gfp_mask, bool noswap,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ec4dcf1b9562..ddffeeda2d52 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1793,6 +1793,7 @@ static void mem_cgroup_out_of_memory(struct mem_cgroup *memcg, gfp_t gfp_mask,
 }
 
 static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
+					unsigned long nr_pages,
 					gfp_t gfp_mask,
 					unsigned long flags)
 {
@@ -1808,7 +1809,8 @@ static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
 	for (loop = 0; loop < MEM_CGROUP_MAX_RECLAIM_LOOPS; loop++) {
 		if (loop)
 			drain_all_stock_async(memcg);
-		total += try_to_free_mem_cgroup_pages(memcg, gfp_mask, noswap);
+		total += try_to_free_mem_cgroup_pages(memcg, nr_pages,
+						      gfp_mask, noswap);
 		/*
 		 * Allow limit shrinkers, which are triggered directly
 		 * by userspace, to catch signals and stop reclaim
@@ -1816,7 +1818,7 @@ static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
 		 */
 		if (total && (flags & MEM_CGROUP_RECLAIM_SHRINK))
 			break;
-		if (mem_cgroup_margin(memcg))
+		if (mem_cgroup_margin(memcg) >= nr_pages)
 			break;
 		/*
 		 * If nothing was reclaimed after two attempts, there
@@ -2572,7 +2574,8 @@ retry:
 	if (!(gfp_mask & __GFP_WAIT))
 		goto nomem;
 
-	nr_reclaimed = mem_cgroup_reclaim(mem_over_limit, gfp_mask, flags);
+	nr_reclaimed = mem_cgroup_reclaim(mem_over_limit, nr_pages,
+					  gfp_mask, flags);
 
 	if (mem_cgroup_margin(mem_over_limit) >= nr_pages)
 		goto retry;
@@ -3718,7 +3721,7 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg,
 		if (!ret)
 			break;
 
-		mem_cgroup_reclaim(memcg, GFP_KERNEL,
+		mem_cgroup_reclaim(memcg, 1, GFP_KERNEL,
 				   MEM_CGROUP_RECLAIM_SHRINK);
 		curusage = res_counter_read_u64(&memcg->res, RES_USAGE);
 		/* Usage is reduced ? */
@@ -3777,7 +3780,7 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg,
 		if (!ret)
 			break;
 
-		mem_cgroup_reclaim(memcg, GFP_KERNEL,
+		mem_cgroup_reclaim(memcg, 1, GFP_KERNEL,
 				   MEM_CGROUP_RECLAIM_NOSWAP |
 				   MEM_CGROUP_RECLAIM_SHRINK);
 		curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);
@@ -4028,7 +4031,7 @@ static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
 		if (signal_pending(current))
 			return -EINTR;
 
-		progress = try_to_free_mem_cgroup_pages(memcg, GFP_KERNEL,
+		progress = try_to_free_mem_cgroup_pages(memcg, 1, GFP_KERNEL,
 						false);
 		if (!progress) {
 			nr_retries--;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index d698f4f7b0f2..7db33f100db4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2747,6 +2747,7 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg,
 }
 
 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
+					   unsigned long nr_pages,
 					   gfp_t gfp_mask,
 					   bool noswap)
 {
@@ -2754,7 +2755,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg,
 	unsigned long nr_reclaimed;
 	int nid;
 	struct scan_control sc = {
-		.nr_to_reclaim = SWAP_CLUSTER_MAX,
+		.nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX),
 		.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
 				(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
 		.target_mem_cgroup = memcg,
-- 
2.0.3

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