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When those pages get uncharged, P->vmstats (hierachical) decreases, which is correct, but P->vmstats_percpu (non-hierarchical) also decreases, which is wrong, as those stats were never added to P->vmstats_percpu to begin with. If the reparented memory exceeds the original non-hierarchical memory in P, some arg such as cache which is shown in memory.stat will be zero (if x < 0, it shows 0) To solve this problem, after reparent memcg, we should use cgroup_rstat_updated to add cgrp to rstat updated tree, and then after css refcount == 0, cgroup_rstat_flush is called by css_release_work_fn and css->flags is set as CSS_RELEASED. We propagate state in vmstat_percpu of struct mem_cgroup to its parent if css->flags is CSS_RELEASED. We use reparent_state to record those state and reparent_tag to ensure propagate vmstats_percpu of dying memcg only once. When mem_cgroup_css_rstat_flush is called, we add reparent_state to parent_memcg->vmstats_percpu->state and memcg->vmstgats_percpu->state_prev in locked context. The delta between state and state_prev would not change. So some accumulative value of vmstats_percpu (such as cache in memory.stat) will be shown correctly. And this patch does not produce delta between state and state_prev in vmstats_percpu which will be added to vmstats. Signed-off-by: Cai Xinchen --- kernel/cgroup/cgroup.c | 5 +++++ mm/memcontrol.c | 43 +++++++++++++++++++++++++++++++++++++++++- 2 files changed, 47 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 935e8121b21e..11138ee09a61 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -5384,12 +5384,17 @@ static void css_release_work_fn(struct work_struct *work) container_of(work, struct cgroup_subsys_state, destroy_work); struct cgroup_subsys *ss = css->ss; struct cgroup *cgrp = css->cgroup; + int cpu; mutex_lock(&cgroup_mutex); css->flags |= CSS_RELEASED; list_del_rcu(&css->sibling); + /* update all cgrp rstat because reparent rstat flush */ + for_each_possible_cpu(cpu) + cgroup_rstat_updated(cgrp, cpu); + if (ss) { /* css release path */ if (!list_empty(&css->rstat_css_node)) { diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 77929d08c8c9..658d42dc9820 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -842,6 +842,9 @@ struct memcg_vmstats_percpu { /* Cgroup1: threshold notifications & softlimit tree updates */ unsigned long nr_page_events; unsigned long targets[MEM_CGROUP_NTARGETS]; + + /* Tag for propagate vmstat_percpu, 1 for start, 0 for stop */ + long reparent_tag; }; struct memcg_vmstats { @@ -852,6 +855,9 @@ struct memcg_vmstats { /* Pending child counts during tree propagation */ long state_pending[MEMCG_NR_STAT]; unsigned long events_pending[NR_MEMCG_EVENTS]; + + /* Propagate vmstat_percpu after reparent */ + long reparent_state[MEMCG_NR_STAT]; }; unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx) @@ -5558,6 +5564,17 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css) return -ENOMEM; } +static void set_reparent_tag_for_vmstats(struct mem_cgroup *memcg) +{ + int cpu; + struct memcg_vmstats_percpu *statc; + + for_each_possible_cpu(cpu) { + statc = per_cpu_ptr(memcg->vmstats_percpu, cpu); + WRITE_ONCE(statc->reparent_tag, 1); + } +} + static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) { struct mem_cgroup *memcg = mem_cgroup_from_css(css); @@ -5579,6 +5596,7 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) page_counter_set_low(&memcg->memory, 0); memcg_reparent_objcgs(memcg); + set_reparent_tag_for_vmstats(memcg); memcg_offline_kmem(memcg); reparent_shrinker_deferred(memcg); wb_memcg_offline(memcg); @@ -5653,8 +5671,9 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) struct mem_cgroup *memcg = mem_cgroup_from_css(css); struct mem_cgroup *parent = parent_mem_cgroup(memcg); struct memcg_vmstats_percpu *statc; - long delta, v; + long delta, v, reparent_v; int i, nid; + bool reparent = false; statc = per_cpu_ptr(memcg->vmstats_percpu, cpu); @@ -5668,6 +5687,10 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) if (delta) memcg->vmstats->state_pending[i] = 0; + reparent_v = memcg->vmstats->reparent_state[i]; + if (reparent_v) + memcg->vmstats->reparent_state[i] = 0; + /* Add CPU changes on this level since the last flush */ v = READ_ONCE(statc->state[i]); if (v != statc->state_prev[i]) { @@ -5675,6 +5698,21 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) statc->state_prev[i] = v; } + /* if reparent tag is set, this cgroup is offline and reparent. + * if css->flags & CSS_RELEASED, this cgroup will be released + * soon. We should propagate memcg's vmstats_percpu to its parent. + */ + if (READ_ONCE(statc->reparent_tag) && + css->flags & CSS_RELEASED && parent) { + parent->vmstats->reparent_state[i] += v + reparent_v; + reparent = true; + } else if (reparent_v) { + __this_cpu_add(memcg->vmstats_percpu->state[i], + reparent_v); + __this_cpu_add(memcg->vmstats_percpu->state_prev[i], + reparent_v); + } + if (!delta) continue; @@ -5684,6 +5722,9 @@ static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) parent->vmstats->state_pending[i] += delta; } + if (reparent) + WRITE_ONCE(statc->reparent_tag, 0); + for (i = 0; i < NR_MEMCG_EVENTS; i++) { delta = memcg->vmstats->events_pending[i]; if (delta) -- 2.17.1