From ce00a967377baadf2481521e131771adc7652856 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Fri, 5 Sep 2014 08:43:57 -0400 Subject: [PATCH] mm: memcontrol: revert use of root_mem_cgroup res_counter Dave Hansen reports a massive scalability regression in an uncontained page fault benchmark with more than 30 concurrent threads, which he bisected down to 05b843012335 ("mm: memcontrol: use root_mem_cgroup res_counter") and pin-pointed on res_counter spinlock contention. That change relied on the per-cpu charge caches to mostly swallow the res_counter costs, but it's apparent that the caches don't scale yet. Revert memcg back to bypassing res_counters on the root level in order to restore performance for uncontained workloads. Reported-by: Dave Hansen Signed-off-by: Johannes Weiner Tested-by: Dave Hansen Acked-by: Michal Hocko Acked-by: Vladimir Davydov Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 103 ++++++++++++++++++++++++++++++++++++------------ 1 file changed, 78 insertions(+), 25 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ec4dcf1b9562..085dc6d2f876 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2534,6 +2534,8 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask, unsigned long long size; int ret = 0; + if (mem_cgroup_is_root(memcg)) + goto done; retry: if (consume_stock(memcg, nr_pages)) goto done; @@ -2611,9 +2613,7 @@ nomem: if (!(gfp_mask & __GFP_NOFAIL)) return -ENOMEM; bypass: - memcg = root_mem_cgroup; - ret = -EINTR; - goto retry; + return -EINTR; done_restock: if (batch > nr_pages) @@ -2626,6 +2626,9 @@ static void cancel_charge(struct mem_cgroup *memcg, unsigned int nr_pages) { unsigned long bytes = nr_pages * PAGE_SIZE; + if (mem_cgroup_is_root(memcg)) + return; + res_counter_uncharge(&memcg->res, bytes); if (do_swap_account) res_counter_uncharge(&memcg->memsw, bytes); @@ -2640,6 +2643,9 @@ static void __mem_cgroup_cancel_local_charge(struct mem_cgroup *memcg, { unsigned long bytes = nr_pages * PAGE_SIZE; + if (mem_cgroup_is_root(memcg)) + return; + res_counter_uncharge_until(&memcg->res, memcg->res.parent, bytes); if (do_swap_account) res_counter_uncharge_until(&memcg->memsw, @@ -4093,6 +4099,46 @@ out: return retval; } +static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *memcg, + enum mem_cgroup_stat_index idx) +{ + struct mem_cgroup *iter; + long val = 0; + + /* Per-cpu values can be negative, use a signed accumulator */ + for_each_mem_cgroup_tree(iter, memcg) + val += mem_cgroup_read_stat(iter, idx); + + if (val < 0) /* race ? */ + val = 0; + return val; +} + +static inline u64 mem_cgroup_usage(struct mem_cgroup *memcg, bool swap) +{ + u64 val; + + if (!mem_cgroup_is_root(memcg)) { + if (!swap) + return res_counter_read_u64(&memcg->res, RES_USAGE); + else + return res_counter_read_u64(&memcg->memsw, RES_USAGE); + } + + /* + * Transparent hugepages are still accounted for in MEM_CGROUP_STAT_RSS + * as well as in MEM_CGROUP_STAT_RSS_HUGE. + */ + val = mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_CACHE); + val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_RSS); + + if (swap) + val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_SWAP); + + return val << PAGE_SHIFT; +} + + static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { @@ -4102,8 +4148,12 @@ static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css, switch (type) { case _MEM: + if (name == RES_USAGE) + return mem_cgroup_usage(memcg, false); return res_counter_read_u64(&memcg->res, name); case _MEMSWAP: + if (name == RES_USAGE) + return mem_cgroup_usage(memcg, true); return res_counter_read_u64(&memcg->memsw, name); case _KMEM: return res_counter_read_u64(&memcg->kmem, name); @@ -4572,10 +4622,7 @@ static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap) if (!t) goto unlock; - if (!swap) - usage = res_counter_read_u64(&memcg->res, RES_USAGE); - else - usage = res_counter_read_u64(&memcg->memsw, RES_USAGE); + usage = mem_cgroup_usage(memcg, swap); /* * current_threshold points to threshold just below or equal to usage. @@ -4673,10 +4720,10 @@ static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg, if (type == _MEM) { thresholds = &memcg->thresholds; - usage = res_counter_read_u64(&memcg->res, RES_USAGE); + usage = mem_cgroup_usage(memcg, false); } else if (type == _MEMSWAP) { thresholds = &memcg->memsw_thresholds; - usage = res_counter_read_u64(&memcg->memsw, RES_USAGE); + usage = mem_cgroup_usage(memcg, true); } else BUG(); @@ -4762,10 +4809,10 @@ static void __mem_cgroup_usage_unregister_event(struct mem_cgroup *memcg, if (type == _MEM) { thresholds = &memcg->thresholds; - usage = res_counter_read_u64(&memcg->res, RES_USAGE); + usage = mem_cgroup_usage(memcg, false); } else if (type == _MEMSWAP) { thresholds = &memcg->memsw_thresholds; - usage = res_counter_read_u64(&memcg->memsw, RES_USAGE); + usage = mem_cgroup_usage(memcg, true); } else BUG(); @@ -5525,9 +5572,9 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css) * core guarantees its existence. */ } else { - res_counter_init(&memcg->res, &root_mem_cgroup->res); - res_counter_init(&memcg->memsw, &root_mem_cgroup->memsw); - res_counter_init(&memcg->kmem, &root_mem_cgroup->kmem); + res_counter_init(&memcg->res, NULL); + res_counter_init(&memcg->memsw, NULL); + res_counter_init(&memcg->kmem, NULL); /* * Deeper hierachy with use_hierarchy == false doesn't make * much sense so let cgroup subsystem know about this @@ -5969,8 +6016,9 @@ static void __mem_cgroup_clear_mc(void) /* we must fixup refcnts and charges */ if (mc.moved_swap) { /* uncharge swap account from the old cgroup */ - res_counter_uncharge(&mc.from->memsw, - PAGE_SIZE * mc.moved_swap); + if (!mem_cgroup_is_root(mc.from)) + res_counter_uncharge(&mc.from->memsw, + PAGE_SIZE * mc.moved_swap); for (i = 0; i < mc.moved_swap; i++) css_put(&mc.from->css); @@ -5979,8 +6027,9 @@ static void __mem_cgroup_clear_mc(void) * we charged both to->res and to->memsw, so we should * uncharge to->res. */ - res_counter_uncharge(&mc.to->res, - PAGE_SIZE * mc.moved_swap); + if (!mem_cgroup_is_root(mc.to)) + res_counter_uncharge(&mc.to->res, + PAGE_SIZE * mc.moved_swap); /* we've already done css_get(mc.to) */ mc.moved_swap = 0; } @@ -6345,7 +6394,8 @@ void mem_cgroup_uncharge_swap(swp_entry_t entry) rcu_read_lock(); memcg = mem_cgroup_lookup(id); if (memcg) { - res_counter_uncharge(&memcg->memsw, PAGE_SIZE); + if (!mem_cgroup_is_root(memcg)) + res_counter_uncharge(&memcg->memsw, PAGE_SIZE); mem_cgroup_swap_statistics(memcg, false); css_put(&memcg->css); } @@ -6509,12 +6559,15 @@ static void uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout, { unsigned long flags; - if (nr_mem) - res_counter_uncharge(&memcg->res, nr_mem * PAGE_SIZE); - if (nr_memsw) - res_counter_uncharge(&memcg->memsw, nr_memsw * PAGE_SIZE); - - memcg_oom_recover(memcg); + if (!mem_cgroup_is_root(memcg)) { + if (nr_mem) + res_counter_uncharge(&memcg->res, + nr_mem * PAGE_SIZE); + if (nr_memsw) + res_counter_uncharge(&memcg->memsw, + nr_memsw * PAGE_SIZE); + memcg_oom_recover(memcg); + } local_irq_save(flags); __this_cpu_sub(memcg->stat->count[MEM_CGROUP_STAT_RSS], nr_anon);