Messages in this thread | | | Date | Thu, 4 Feb 2010 13:57:43 +0530 | From | Balbir Singh <> | Subject | Re: [PATCH] memcg: use for each online for making sum of percpu counter |
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* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-02-04 14:36:45]:
> 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++) {
Should we add a for_each_stat_idx() macro?
> + val = per_cpu(memcg->stat->count[idx], cpu); > + per_cpu(memcg->stat->count[idx], cpu) = 0; > + this_cpu_add(memcg->stat->count[idx], val);
So the CPU that deals with the hotplug notification moves the stats to its own counter? Seems fair enough.
> + } > + } > + 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; >
Looks good, but I've not tested it yet.
-- Balbir
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