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Commit 0ae5e89c authored by Ying Han's avatar Ying Han Committed by Linus Torvalds
Browse files

memcg: count the soft_limit reclaim in global background reclaim 



The global kswapd scans per-zone LRU and reclaims pages regardless of the
cgroup. It breaks memory isolation since one cgroup can end up reclaiming
pages from another cgroup. Instead we should rely on memcg-aware target
reclaim including per-memcg kswapd and soft_limit hierarchical reclaim under
memory pressure.

In the global background reclaim, we do soft reclaim before scanning the
per-zone LRU. However, the return value is ignored. This patch is the first
step to skip shrink_zone() if soft_limit reclaim does enough work.

This is part of the effort which tries to reduce reclaiming pages in global
LRU in memcg. The per-memcg background reclaim patchset further enhances the
per-cgroup targetting reclaim, which I should have V4 posted shortly.

Try running multiple memory intensive workloads within seperate memcgs. Watch
the counters of soft_steal in memory.stat.

  $ cat /dev/cgroup/A/memory.stat | grep 'soft'
  soft_steal 240000
  soft_scan 240000
  total_soft_steal 240000
  total_soft_scan 240000

This patch:

In the global background reclaim, we do soft reclaim before scanning the
per-zone LRU.  However, the return value is ignored.

We would like to skip shrink_zone() if soft_limit reclaim does enough
work.  Also, we need to make the memory pressure balanced across per-memcg
zones, like the logic vm-core.  This patch is the first step where we
start with counting the nr_scanned and nr_reclaimed from soft_limit
reclaim into the global scan_control.

Signed-off-by: default avatarYing Han <yinghan@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Acked-by: default avatarDaisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f042e707

include/linux/memcontrol.h

+4 −2
Original line number Diff line number Diff line
@@ -144,7 +144,8 @@ static inline void mem_cgroup_dec_page_stat(struct page *page, 
}



unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,

						gfp_t gfp_mask);

						gfp_t gfp_mask,

						unsigned long *total_scanned);

u64 mem_cgroup_get_limit(struct mem_cgroup *mem);



#ifdef CONFIG_TRANSPARENT_HUGEPAGE
@@ -338,7 +339,8 @@ static inline void mem_cgroup_dec_page_stat(struct page *page, 


static inline

unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,

					    gfp_t gfp_mask)

					    gfp_t gfp_mask,

					    unsigned long *total_scanned)

{

	return 0;

}

include/linux/swap.h

+2 −1
Original line number Diff line number Diff line
@@ -257,7 +257,8 @@ extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem, 
extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,

						gfp_t gfp_mask, bool noswap,

						unsigned int swappiness,

						struct zone *zone);

						struct zone *zone,

						unsigned long *nr_scanned);

extern int __isolate_lru_page(struct page *page, int mode, int file);

extern unsigned long shrink_all_memory(unsigned long nr_pages);

extern int vm_swappiness;

mm/memcontrol.c

+20 −9
Original line number Diff line number Diff line
@@ -1433,7 +1433,8 @@ mem_cgroup_select_victim(struct mem_cgroup *root_mem) 
static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,

						struct zone *zone,

						gfp_t gfp_mask,

						unsigned long reclaim_options)

						unsigned long reclaim_options,

						unsigned long *total_scanned)

{

	struct mem_cgroup *victim;

	int ret, total = 0;
@@ -1442,6 +1443,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem, 
	bool shrink = reclaim_options & MEM_CGROUP_RECLAIM_SHRINK;

	bool check_soft = reclaim_options & MEM_CGROUP_RECLAIM_SOFT;

	unsigned long excess;

	unsigned long nr_scanned;



	excess = res_counter_soft_limit_excess(&root_mem->res) >> PAGE_SHIFT;
@@ -1484,10 +1486,12 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem, 
			continue;

		}

		/* we use swappiness of local cgroup */

		if (check_soft)

		if (check_soft) {

			ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,

				noswap, get_swappiness(victim), zone);

		else

				noswap, get_swappiness(victim), zone,

				&nr_scanned);

			*total_scanned += nr_scanned;

		} else

			ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,

						noswap, get_swappiness(victim));

		css_put(&victim->css);
@@ -1928,7 +1932,7 @@ static int mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask, 
		return CHARGE_WOULDBLOCK;



	ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,

					      gfp_mask, flags);

					      gfp_mask, flags, NULL);

	if (mem_cgroup_margin(mem_over_limit) >= nr_pages)

		return CHARGE_RETRY;

	/*
@@ -3211,7 +3215,8 @@ static int mem_cgroup_resize_limit(struct mem_cgroup *memcg, 
			break;



		mem_cgroup_hierarchical_reclaim(memcg, NULL, GFP_KERNEL,

						MEM_CGROUP_RECLAIM_SHRINK);

						MEM_CGROUP_RECLAIM_SHRINK,

						NULL);

		curusage = res_counter_read_u64(&memcg->res, RES_USAGE);

		/* Usage is reduced ? */

  		if (curusage >= oldusage)
@@ -3271,7 +3276,8 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg, 


		mem_cgroup_hierarchical_reclaim(memcg, NULL, GFP_KERNEL,

						MEM_CGROUP_RECLAIM_NOSWAP |

						MEM_CGROUP_RECLAIM_SHRINK);

						MEM_CGROUP_RECLAIM_SHRINK,

						NULL);

		curusage = res_counter_read_u64(&memcg->memsw, RES_USAGE);

		/* Usage is reduced ? */

		if (curusage >= oldusage)
@@ -3285,7 +3291,8 @@ static int mem_cgroup_resize_memsw_limit(struct mem_cgroup *memcg, 
}



unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,

					    gfp_t gfp_mask)

					    gfp_t gfp_mask,

					    unsigned long *total_scanned)

{

	unsigned long nr_reclaimed = 0;

	struct mem_cgroup_per_zone *mz, *next_mz = NULL;
@@ -3293,6 +3300,7 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order, 
	int loop = 0;

	struct mem_cgroup_tree_per_zone *mctz;

	unsigned long long excess;

	unsigned long nr_scanned;



	if (order > 0)

		return 0;
@@ -3311,10 +3319,13 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order, 
		if (!mz)

			break;



		nr_scanned = 0;

		reclaimed = mem_cgroup_hierarchical_reclaim(mz->mem, zone,

						gfp_mask,

						MEM_CGROUP_RECLAIM_SOFT);

						MEM_CGROUP_RECLAIM_SOFT,

						&nr_scanned);

		nr_reclaimed += reclaimed;

		*total_scanned += nr_scanned;

		spin_lock(&mctz->lock);



		/*

mm/vmscan.c

+13 −3
Original line number Diff line number Diff line
@@ -2171,9 +2171,11 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, 
unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,

						gfp_t gfp_mask, bool noswap,

						unsigned int swappiness,

						struct zone *zone)

						struct zone *zone,

						unsigned long *nr_scanned)

{

	struct scan_control sc = {

		.nr_scanned = 0,

		.nr_to_reclaim = SWAP_CLUSTER_MAX,

		.may_writepage = !laptop_mode,

		.may_unmap = 1,
@@ -2182,6 +2184,7 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 
		.order = 0,

		.mem_cgroup = mem,

	};



	sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |

			(GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
@@ -2200,6 +2203,7 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, 


	trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);



	*nr_scanned = sc.nr_scanned;

	return sc.nr_reclaimed;

}
@@ -2347,6 +2351,8 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 
	int end_zone = 0;	/* Inclusive.  0 = ZONE_DMA */

	unsigned long total_scanned;

	struct reclaim_state *reclaim_state = current->reclaim_state;

	unsigned long nr_soft_reclaimed;

	unsigned long nr_soft_scanned;

	struct scan_control sc = {

		.gfp_mask = GFP_KERNEL,

		.may_unmap = 1,
@@ -2439,11 +2445,15 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, int order, 


			sc.nr_scanned = 0;



			nr_soft_scanned = 0;

			/*

			 * Call soft limit reclaim before calling shrink_zone.

			 * For now we ignore the return value

			 */

			mem_cgroup_soft_limit_reclaim(zone, order, sc.gfp_mask);

			nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone,

							order, sc.gfp_mask,

							&nr_soft_scanned);

			sc.nr_reclaimed += nr_soft_reclaimed;

			total_scanned += nr_soft_scanned;



			/*

			 * We put equal pressure on every zone, unless