Messages in this thread Patch in this message | | | Date | Thu, 4 Feb 2010 14:36:45 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [PATCH] memcg: use for each online for making sum of percpu counter |
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Tested on mmotm-2010-02-03.
Balbir-san, how about this patch ? It seems not so difficult as expected.
== From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
memcg-use-for-each-online-cpus-for-making-sum-of-percpu-counter
Now, memcg's percpu coutner uses for_each_possible_cpus() for handling cpu hotplug. But it adds some overhead on a server which has an additonal cpu hotplug slot which is not used.
This patch adds cpu hotplug callback for memcg's percpu counter and make use of for_each_online_cpu().
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- mm/memcontrol.c | 35 ++++++++++++++++++++++++++++++++--- 1 file changed, 32 insertions(+), 3 deletions(-)
Index: mmotm-2.6.33-Feb3/mm/memcontrol.c =================================================================== --- mmotm-2.6.33-Feb3.orig/mm/memcontrol.c +++ mmotm-2.6.33-Feb3/mm/memcontrol.c @@ -223,6 +223,8 @@ struct mem_cgroup { */ unsigned long move_charge_at_immigrate; + /* list of all memcgs. currently used for cpu hotplug+percpu counter */ + struct list_head list; /* * percpu counter. */ @@ -504,7 +506,7 @@ static s64 mem_cgroup_read_stat(struct m int cpu; s64 val = 0; - for_each_possible_cpu(cpu) + for_each_online_cpu(cpu) val += per_cpu(mem->stat->count[idx], cpu); return val; } @@ -1405,17 +1407,37 @@ static void drain_all_stock_sync(void) atomic_dec(&memcg_drain_count); } -static int __cpuinit memcg_stock_cpu_callback(struct notifier_block *nb, +DEFINE_MUTEX(memcg_hotcpu_lock); +LIST_HEAD(memcg_hotcpu_list); + +static int __cpuinit memcg_cpu_unplug_callback(struct notifier_block *nb, unsigned long action, void *hcpu) { int cpu = (unsigned long)hcpu; + struct mem_cgroup *memcg; struct memcg_stock_pcp *stock; + int idx; + s64 val; if (action != CPU_DEAD) return NOTIFY_OK; stock = &per_cpu(memcg_stock, cpu); drain_stock(stock); + + /* Move dead percpu counter's value to online cpu */ + mutex_lock(&memcg_hotcpu_lock); + list_for_each_entry(memcg, &memcg_hotcpu_list, list) { + for (idx = MEM_CGROUP_STAT_CACHE; + idx <= MEM_CGROUP_STAT_SWAPOUT; + idx++) { + val = per_cpu(memcg->stat->count[idx], cpu); + per_cpu(memcg->stat->count[idx], cpu) = 0; + this_cpu_add(memcg->stat->count[idx], val); + } + } + mutex_unlock(&memcg_hotcpu_lock); + return NOTIFY_OK; } @@ -3626,6 +3648,10 @@ static struct mem_cgroup *mem_cgroup_all else vfree(mem); mem = NULL; + } else { + mutex_lock(&memcg_hotcpu_lock); + list_add(&mem->list, &memcg_hotcpu_list); + mutex_unlock(&memcg_hotcpu_lock); } return mem; } @@ -3651,6 +3677,9 @@ static void __mem_cgroup_free(struct mem for_each_node_state(node, N_POSSIBLE) free_mem_cgroup_per_zone_info(mem, node); + mutex_lock(&memcg_hotcpu_lock); + list_del(&mem->list); + mutex_unlock(&memcg_hotcpu_lock); free_percpu(mem->stat); if (sizeof(struct mem_cgroup) < PAGE_SIZE) kfree(mem); @@ -3753,7 +3782,7 @@ mem_cgroup_create(struct cgroup_subsys * &per_cpu(memcg_stock, cpu); INIT_WORK(&stock->work, drain_local_stock); } - hotcpu_notifier(memcg_stock_cpu_callback, 0); + hotcpu_notifier(memcg_cpu_unplug_callback, 0); } else { parent = mem_cgroup_from_cont(cont->parent); mem->use_hierarchy = parent->use_hierarchy;
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