On Sat 19-01-19 22:30:18, Xiongchun Duan wrote:
> Add timer to trigger workqueue which will scan offline memcgroup and call trigger
> memcgroup force_empty worker to force_empty itself.
This requires much more explanation but it looks like a complete hack to
me. Why do we need a timer at all? Why is the hardcoded timeout a
generic enough?
> Signed-off-by: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx>
> ---
> include/linux/memcontrol.h | 1 +
> mm/memcontrol.c | 23 +++++++++++++++++++++++
> 2 files changed, 24 insertions(+)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index d6fbb77..0a29f7f 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -313,6 +313,7 @@ struct mem_cgroup {
>
> int max_retry;
> int current_retry;
> + unsigned long timer_jiffies;
>
> struct mem_cgroup_per_node *nodeinfo[0];
> /* WARNING: nodeinfo must be the last member here */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2b13c2b..4db08b7 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -81,6 +81,8 @@
> int sysctl_cgroup_default_retry_min;
> int sysctl_cgroup_default_retry_max = 16;
>
> +struct timer_list empty_trigger;
> +
> struct mem_cgroup *root_mem_cgroup __read_mostly;
>
> #define MEM_CGROUP_RECLAIM_RETRIES 5
> @@ -2933,6 +2935,11 @@ static ssize_t mem_cgroup_force_empty_write(struct kernfs_open_file *of,
> return mem_cgroup_force_empty(memcg) ?: nbytes;
> }
>
> +static void add_force_empty_list(struct mem_cgroup *memcg)
> +{
> +
> +}
> +
> static u64 mem_cgroup_hierarchy_read(struct cgroup_subsys_state *css,
> struct cftype *cft)
> {
> @@ -4566,11 +4573,26 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
> return 0;
> }
>
> +void empty_timer_trigger(struct timer_list *t)
> +{
> +
> +}
> +
> static void mem_cgroup_css_offline(struct cgroup_subsys_state *css)
> {
> struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> struct mem_cgroup_event *event, *tmp;
>
> + if (memcg->max_retry != 0) {
> + memcg->current_retry = 1;
> + mem_cgroup_force_empty(memcg);
> + if (page_counter_read(&memcg->memory) &&
> + memcg->max_retry != 1) {
> + memcg->timer_jiffies = jiffies + HZ;
> + add_force_empty_list(memcg);
> + }
> + }
> +
> /*
> * Unregister events and notify userspace.
> * Notify userspace about cgroup removing only after rmdir of cgroup
> @@ -6368,6 +6390,7 @@ static int __init mem_cgroup_init(void)
> memcg_kmem_cache_wq = alloc_workqueue("memcg_kmem_cache", 0, 1);
> BUG_ON(!memcg_kmem_cache_wq);
> #endif
> + timer_setup(&empty_trigger, empty_timer_trigger, 0);
>
> cpuhp_setup_state_nocalls(CPUHP_MM_MEMCQ_DEAD, "mm/memctrl:dead", NULL,
> memcg_hotplug_cpu_dead);
> --
> 1.8.3.1
--
Michal Hocko
SUSE Labs
