On Thu, Apr 12, 2012 at 4:28 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> Now, at rmdir, memory cgroup's charge will be moved to
> - parent if use_hierarchy=1
> - root if use_hierarchy=0
>
> Then, we don't have to have memory reclaim code at destroying memcg.
>
> This patch divides force_empty to 2 functions as
>
> - memory_cgroup_recharge() ... try to move all charges to ancestors.
> - memory_cgroup_force_empty().. try to reclaim all memory.
>
> After this patch, memory.force_empty will _not_ move charges to ancestors
> but just reclaim all pages. (This meets documenation.)
Not sure why it matches the documentation:
"
memory.force_empty>---->------- # trigger forced move charge to parent
"
and
"
# echo 0 > memory.force_empty
Almost all pages tracked by this memory cgroup will be unmapped and freed.
Some pages cannot be freed because they are locked or in-use. Such pages are
moved to parent and this cgroup will be empty. This may return -EBUSY if
VM is too busy to free/move all pages immediately.
"
--Ying
>
> rmdir() will not reclaim any memory but moves charge to other cgroup,
> parent or root.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> mm/memcontrol.c | 59 +++++++++++++++++++++++++++----------------------------
> 1 files changed, 29 insertions(+), 30 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 9ac7984..22c8faa 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3619,10 +3619,9 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> }
>
> /*
> - * This routine traverse page_cgroup in given list and drop them all.
> - * *And* this routine doesn't reclaim page itself, just removes page_cgroup.
> + * This routine traverse page in given list and move them all.
> */
> -static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
> +static int mem_cgroup_recharge_lru(struct mem_cgroup *memcg,
> int node, int zid, enum lru_list lru)
> {
> struct mem_cgroup_per_zone *mz;
> @@ -3678,24 +3677,12 @@ static int mem_cgroup_force_empty_list(struct mem_cgroup *memcg,
> return ret;
> }
>
> -/*
> - * make mem_cgroup's charge to be 0 if there is no task.
> - * This enables deleting this mem_cgroup.
> - */
> -static int mem_cgroup_force_empty(struct mem_cgroup *memcg, bool free_all)
> +
> +static int mem_cgroup_recharge(struct mem_cgroup *memcg)
> {
> - int ret;
> - int node, zid, shrink;
> - int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> + int ret, node, zid;
> struct cgroup *cgrp = memcg->css.cgroup;
>
> - css_get(&memcg->css);
> -
> - shrink = 0;
> - /* should free all ? */
> - if (free_all)
> - goto try_to_free;
> -move_account:
> do {
> ret = -EBUSY;
> if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children))
> @@ -3712,7 +3699,7 @@ move_account:
> for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
> enum lru_list lru;
> for_each_lru(lru) {
> - ret = mem_cgroup_force_empty_list(memcg,
> + ret = mem_cgroup_recharge_lru(memcg,
> node, zid, lru);
> if (ret)
> break;
> @@ -3722,24 +3709,33 @@ move_account:
> break;
> }
> mem_cgroup_end_move(memcg);
> - memcg_oom_recover(memcg);
> cond_resched();
> /* "ret" should also be checked to ensure all lists are empty. */
> } while (memcg->res.usage > 0 || ret);
> out:
> - css_put(&memcg->css);
> return ret;
> +}
> +
> +
> +/*
> + * make mem_cgroup's charge to be 0 if there is no task. This is only called
> + * by memory.force_empty file, an user request.
> + */
> +static int mem_cgroup_force_empty(struct mem_cgroup *memcg)
> +{
> + int ret = 0;
> + int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
> + struct cgroup *cgrp = memcg->css.cgroup;
> +
> + css_get(&memcg->css);
>
> -try_to_free:
> /* returns EBUSY if there is a task or if we come here twice. */
> - if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children) || shrink) {
> + if (cgroup_task_count(cgrp) || !list_empty(&cgrp->children)) {
> ret = -EBUSY;
> goto out;
> }
> /* we call try-to-free pages for make this cgroup empty */
> lru_add_drain_all();
> - /* try to free all pages in this cgroup */
> - shrink = 1;
> while (nr_retries && memcg->res.usage > 0) {
> int progress;
>
> @@ -3754,16 +3750,19 @@ try_to_free:
> /* maybe some writeback is necessary */
> congestion_wait(BLK_RW_ASYNC, HZ/10);
> }
> -
> }
> - lru_add_drain();
> + if (!nr_retries)
> + ret = -ENOMEM;
> +out:
> + memcg_oom_recover(memcg);
> + css_put(&memcg->css);
> /* try move_account...there may be some *locked* pages. */
> - goto move_account;
> + return ret;
> }
>
> int mem_cgroup_force_empty_write(struct cgroup *cont, unsigned int event)
> {
> - return mem_cgroup_force_empty(mem_cgroup_from_cont(cont), true);
> + return mem_cgroup_force_empty(mem_cgroup_from_cont(cont));
> }
>
>
> @@ -4987,7 +4986,7 @@ static int mem_cgroup_pre_destroy(struct cgroup *cont)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
>
> - return mem_cgroup_force_empty(memcg, false);
> + return mem_cgroup_recharge(memcg);
> }
>
> static void mem_cgroup_destroy(struct cgroup *cont)
> --
> 1.7.4.1
>
>
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