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: Ying 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: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fc25992..e41a6c2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1433,7 +1433,8 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
}
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 @@
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 @@
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);
/*