From: Shakeel Butt shakeelb@google.com
commit fd25a9e0e23b995fd0ba5e2f00a1099452cbc3cf upstream.
The memcg stats can be flushed in multiple context and potentially in parallel too. For example multiple parallel user space readers for memcg stats will contend on the rstat locks with each other. There is no need for that. We just need one flusher and everyone else can benefit.
In addition after aa48e47e3906 ("memcg: infrastructure to flush memcg stats") the kernel periodically flush the memcg stats from the root, so, the other flushers will potentially have much less work to do.
Link: https://lkml.kernel.org/r/20211001190040.48086-2-shakeelb@google.com Signed-off-by: Shakeel Butt shakeelb@google.com Acked-by: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@kernel.org Cc: "Michal Koutný" mkoutny@suse.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Cc: Ivan Babrou ivan@cloudflare.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/memcontrol.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-)
--- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -660,12 +660,14 @@ static inline void memcg_rstat_updated(s
static void __mem_cgroup_flush_stats(void) { - if (!spin_trylock(&stats_flush_lock)) + unsigned long flag; + + if (!spin_trylock_irqsave(&stats_flush_lock, flag)) return;
cgroup_rstat_flush_irqsafe(root_mem_cgroup->css.cgroup); atomic_set(&stats_flush_threshold, 0); - spin_unlock(&stats_flush_lock); + spin_unlock_irqrestore(&stats_flush_lock, flag); }
void mem_cgroup_flush_stats(void) @@ -1461,7 +1463,7 @@ static char *memory_stat_format(struct m * * Current memory state: */ - cgroup_rstat_flush(memcg->css.cgroup); + mem_cgroup_flush_stats();
for (i = 0; i < ARRAY_SIZE(memory_stats); i++) { u64 size; @@ -3554,8 +3556,7 @@ static unsigned long mem_cgroup_usage(st unsigned long val;
if (mem_cgroup_is_root(memcg)) { - /* mem_cgroup_threshold() calls here from irqsafe context */ - cgroup_rstat_flush_irqsafe(memcg->css.cgroup); + mem_cgroup_flush_stats(); val = memcg_page_state(memcg, NR_FILE_PAGES) + memcg_page_state(memcg, NR_ANON_MAPPED); if (swap) @@ -3936,7 +3937,7 @@ static int memcg_numa_stat_show(struct s int nid; struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
- cgroup_rstat_flush(memcg->css.cgroup); + mem_cgroup_flush_stats();
for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) { seq_printf(m, "%s=%lu", stat->name, @@ -4008,7 +4009,7 @@ static int memcg_stat_show(struct seq_fi
BUILD_BUG_ON(ARRAY_SIZE(memcg1_stat_names) != ARRAY_SIZE(memcg1_stats));
- cgroup_rstat_flush(memcg->css.cgroup); + mem_cgroup_flush_stats();
for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) { unsigned long nr; @@ -4511,7 +4512,7 @@ void mem_cgroup_wb_stats(struct bdi_writ struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css); struct mem_cgroup *parent;
- cgroup_rstat_flush_irqsafe(memcg->css.cgroup); + mem_cgroup_flush_stats();
*pdirty = memcg_page_state(memcg, NR_FILE_DIRTY); *pwriteback = memcg_page_state(memcg, NR_WRITEBACK); @@ -6394,7 +6395,7 @@ static int memory_numa_stat_show(struct int i; struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
- cgroup_rstat_flush(memcg->css.cgroup); + mem_cgroup_flush_stats();
for (i = 0; i < ARRAY_SIZE(memory_stats); i++) { int nid;