Re: [PATCH 2/3] weight for memcg background reclaim (Was Re: [PATCH V6 00/10] memcg: per cgroup background reclaim

[Ying Han <yinghan@google.com>]

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On Wed, Apr 20, 2011 at 8:48 PM, KAMEZAWA Hiroyuki <
kamezawa.hiroyu@jp.fujitsu.com> wrote:

>
> memcg-kswapd visits each memcg in round-robin. But required
> amounts of works depends on memcg' usage and hi/low watermark
> and taking it into account will be good.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  include/linux/memcontrol.h |    1 +
>  mm/memcontrol.c            |   17 +++++++++++++++++
>  mm/vmscan.c                |    2 ++
>  3 files changed, 20 insertions(+)
>
> Index: mmotm-Apr14/include/linux/memcontrol.h
> ===================================================================
> --- mmotm-Apr14.orig/include/linux/memcontrol.h
> +++ mmotm-Apr14/include/linux/memcontrol.h
> @@ -98,6 +98,7 @@ extern bool mem_cgroup_kswapd_can_sleep(
>  extern struct mem_cgroup *mem_cgroup_get_shrink_target(void);
>  extern void mem_cgroup_put_shrink_target(struct mem_cgroup *mem);
>  extern wait_queue_head_t *mem_cgroup_kswapd_waitq(void);
> +extern int mem_cgroup_kswapd_bonus(struct mem_cgroup *mem);
>
>  static inline
>  int mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup
> *cgroup)
> Index: mmotm-Apr14/mm/memcontrol.c
> ===================================================================
> --- mmotm-Apr14.orig/mm/memcontrol.c
> +++ mmotm-Apr14/mm/memcontrol.c
> @@ -4673,6 +4673,23 @@ struct memcg_kswapd_work
>
>  struct memcg_kswapd_work       memcg_kswapd_control;
>
> +int mem_cgroup_kswapd_bonus(struct mem_cgroup *mem)
> +{
> +       unsigned long long usage, lowat, hiwat;
> +       int rate;
> +
> +       usage = res_counter_read_u64(&mem->res, RES_USAGE);
> +       lowat = res_counter_read_u64(&mem->res, RES_LOW_WMARK_LIMIT);
> +       hiwat = res_counter_read_u64(&mem->res, RES_HIGH_WMARK_LIMIT);
> +       if (lowat == hiwat)
> +               return 0;
> +
> +       rate = (usage - hiwat) * 10 / (lowat - hiwat);
> +       /* If usage is big, we reclaim more */
> +       return rate * SWAP_CLUSTER_MAX;
> +}
> +
>


> I understand the logic in general, which we would like to reclaim more each
> time if more work needs to be done. But not quite sure the calculation here,
> the (usage - hiwat) determines the amount of work of kswapd. And why divide
> by (lowat - hiwat)? My guess is because the larger the value, the later we
> will trigger kswapd?


--Ying



>


>


>  static void wake_memcg_kswapd(struct mem_cgroup *mem)
>  {
>        if (atomic_read(&mem->kswapd_running)) /* already running */
> Index: mmotm-Apr14/mm/vmscan.c
> ===================================================================
> --- mmotm-Apr14.orig/mm/vmscan.c
> +++ mmotm-Apr14/mm/vmscan.c
> @@ -2732,6 +2732,8 @@ static int shrink_mem_cgroup(struct mem_
>        sc.nr_reclaimed = 0;
>        total_scanned = 0;
>
> +       sc.nr_to_reclaim += mem_cgroup_kswapd_bonus(mem_cont);
> +
>        do_nodes = node_states[N_ONLINE];
>
>        for (priority = DEF_PRIORITY;
>
>

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