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authorJohannes Weiner <hannes@cmpxchg.org>2018-04-10 16:29:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-04-11 10:28:31 -0700
commite27be240df53f1a20c659168e722b5d9f16cc7f4 (patch)
tree13cbd6310d17479f45528f93721c779419bffa21 /mm
parenta38c015f3156895b07e71d4e4414289f8a3b2745 (diff)
mm: memcg: make sure memory.events is uptodate when waking pollers
Commit a983b5ebee57 ("mm: memcontrol: fix excessive complexity in memory.stat reporting") added per-cpu drift to all memory cgroup stats and events shown in memory.stat and memory.events. For memory.stat this is acceptable. But memory.events issues file notifications, and somebody polling the file for changes will be confused when the counters in it are unchanged after a wakeup. Luckily, the events in memory.events - MEMCG_LOW, MEMCG_HIGH, MEMCG_MAX, MEMCG_OOM - are sufficiently rare and high-level that we don't need per-cpu buffering for them: MEMCG_HIGH and MEMCG_MAX would be the most frequent, but they're counting invocations of reclaim, which is a complex operation that touches many shared cachelines. This splits memory.events from the generic VM events and tracks them in their own, unbuffered atomic counters. That's also cleaner, as it eliminates the ugly enum nesting of VM and cgroup events. [hannes@cmpxchg.org: "array subscript is above array bounds"] Link: http://lkml.kernel.org/r/20180406155441.GA20806@cmpxchg.org Link: http://lkml.kernel.org/r/20180405175507.GA24817@cmpxchg.org Fixes: a983b5ebee57 ("mm: memcontrol: fix excessive complexity in memory.stat reporting") Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Reported-by: Tejun Heo <tj@kernel.org> Acked-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Cc: Roman Gushchin <guro@fb.com> Cc: Rik van Riel <riel@surriel.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c28
-rw-r--r--mm/vmscan.c2
2 files changed, 17 insertions, 13 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6b4f5c0a8eef..f314334546a2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1839,7 +1839,7 @@ static int memcg_hotplug_cpu_dead(unsigned int cpu)
}
}
- for (i = 0; i < MEMCG_NR_EVENTS; i++) {
+ for (i = 0; i < NR_VM_EVENT_ITEMS; i++) {
long x;
x = this_cpu_xchg(memcg->stat_cpu->events[i], 0);
@@ -1858,7 +1858,7 @@ static void reclaim_high(struct mem_cgroup *memcg,
do {
if (page_counter_read(&memcg->memory) <= memcg->high)
continue;
- mem_cgroup_event(memcg, MEMCG_HIGH);
+ memcg_memory_event(memcg, MEMCG_HIGH);
try_to_free_mem_cgroup_pages(memcg, nr_pages, gfp_mask, true);
} while ((memcg = parent_mem_cgroup(memcg)));
}
@@ -1949,7 +1949,7 @@ retry:
if (!gfpflags_allow_blocking(gfp_mask))
goto nomem;
- mem_cgroup_event(mem_over_limit, MEMCG_MAX);
+ memcg_memory_event(mem_over_limit, MEMCG_MAX);
nr_reclaimed = try_to_free_mem_cgroup_pages(mem_over_limit, nr_pages,
gfp_mask, may_swap);
@@ -1992,7 +1992,7 @@ retry:
if (fatal_signal_pending(current))
goto force;
- mem_cgroup_event(mem_over_limit, MEMCG_OOM);
+ memcg_memory_event(mem_over_limit, MEMCG_OOM);
mem_cgroup_oom(mem_over_limit, gfp_mask,
get_order(nr_pages * PAGE_SIZE));
@@ -2688,10 +2688,10 @@ static void tree_events(struct mem_cgroup *memcg, unsigned long *events)
struct mem_cgroup *iter;
int i;
- memset(events, 0, sizeof(*events) * MEMCG_NR_EVENTS);
+ memset(events, 0, sizeof(*events) * NR_VM_EVENT_ITEMS);
for_each_mem_cgroup_tree(iter, memcg) {
- for (i = 0; i < MEMCG_NR_EVENTS; i++)
+ for (i = 0; i < NR_VM_EVENT_ITEMS; i++)
events[i] += memcg_sum_events(iter, i);
}
}
@@ -5178,7 +5178,7 @@ static ssize_t memory_max_write(struct kernfs_open_file *of,
continue;
}
- mem_cgroup_event(memcg, MEMCG_OOM);
+ memcg_memory_event(memcg, MEMCG_OOM);
if (!mem_cgroup_out_of_memory(memcg, GFP_KERNEL, 0))
break;
}
@@ -5191,10 +5191,14 @@ static int memory_events_show(struct seq_file *m, void *v)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
- seq_printf(m, "low %lu\n", memcg_sum_events(memcg, MEMCG_LOW));
- seq_printf(m, "high %lu\n", memcg_sum_events(memcg, MEMCG_HIGH));
- seq_printf(m, "max %lu\n", memcg_sum_events(memcg, MEMCG_MAX));
- seq_printf(m, "oom %lu\n", memcg_sum_events(memcg, MEMCG_OOM));
+ seq_printf(m, "low %lu\n",
+ atomic_long_read(&memcg->memory_events[MEMCG_LOW]));
+ seq_printf(m, "high %lu\n",
+ atomic_long_read(&memcg->memory_events[MEMCG_HIGH]));
+ seq_printf(m, "max %lu\n",
+ atomic_long_read(&memcg->memory_events[MEMCG_MAX]));
+ seq_printf(m, "oom %lu\n",
+ atomic_long_read(&memcg->memory_events[MEMCG_OOM]));
seq_printf(m, "oom_kill %lu\n", memcg_sum_events(memcg, OOM_KILL));
return 0;
@@ -5204,7 +5208,7 @@ static int memory_stat_show(struct seq_file *m, void *v)
{
struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
unsigned long stat[MEMCG_NR_STAT];
- unsigned long events[MEMCG_NR_EVENTS];
+ unsigned long events[NR_VM_EVENT_ITEMS];
int i;
/*
diff --git a/mm/vmscan.c b/mm/vmscan.c
index a1d7ba0136fe..671597ce1ea0 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2530,7 +2530,7 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
sc->memcg_low_skipped = 1;
continue;
}
- mem_cgroup_event(memcg, MEMCG_LOW);
+ memcg_memory_event(memcg, MEMCG_LOW);
}
reclaimed = sc->nr_reclaimed;