Re: [PATCH 2/2] memcg : share event counter rather than duplicate v2

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Fri, Feb 12, 2010 at 11:09 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
> Memcg has 2 eventcountes which counts "the same" event. Just usages are
> different from each other. This patch tries to reduce event counter.
>
> Now logic uses "only increment, no reset" counter and masks for each
> checks. Softlimit chesk was done per 1000 evetns. So, the similar check
> can be done by !(new_counter & 0x3ff). Threshold check was done per 100
> events. So, the similar check can be done by (!new_counter & 0x7f)
>
> ALL event checks are done right after EVENT percpu counter is updated.
>
> Changelog: 2010/02/12
>  - fixed to use "inc" rather than "dec"
>  - modified to be more unified style of counter handling.
>  - taking care of account-move.
>
> Cc: Kirill A. Shutemov <kirill@shutemov.name>
> Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  mm/memcontrol.c |   86 ++++++++++++++++++++++++++------------------------------
>  1 file changed, 41 insertions(+), 45 deletions(-)
>
> Index: mmotm-2.6.33-Feb10/mm/memcontrol.c
> ===================================================================
> --- mmotm-2.6.33-Feb10.orig/mm/memcontrol.c
> +++ mmotm-2.6.33-Feb10/mm/memcontrol.c
> @@ -63,8 +63,15 @@ static int really_do_swap_account __init
>  #define do_swap_account                (0)
>  #endif
>
> -#define SOFTLIMIT_EVENTS_THRESH (1000)
> -#define THRESHOLDS_EVENTS_THRESH (100)
> +/*
> + * Per memcg event counter is incremented at every pagein/pageout. This counter
> + * is used for trigger some periodic events. This is straightforward and better
> + * than using jiffies etc. to handle periodic memcg event.
> + *
> + * These values will be used as !((event) & ((1 <<(thresh)) - 1))
> + */
> +#define THRESHOLDS_EVENTS_THRESH (7) /* once in 128 */
> +#define SOFTLIMIT_EVENTS_THRESH (10) /* once in 1024 */
>
>  /*
>  * Statistics for memory cgroup.
> @@ -79,10 +86,7 @@ enum mem_cgroup_stat_index {
>        MEM_CGROUP_STAT_PGPGIN_COUNT,   /* # of pages paged in */
>        MEM_CGROUP_STAT_PGPGOUT_COUNT,  /* # of pages paged out */
>        MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
> -       MEM_CGROUP_STAT_SOFTLIMIT, /* decrements on each page in/out.
> -                                       used by soft limit implementation */
> -       MEM_CGROUP_STAT_THRESHOLDS, /* decrements on each page in/out.
> -                                       used by threshold implementation */
> +       MEM_CGROUP_EVENTS,      /* incremented at every  pagein/pageout */
>
>        MEM_CGROUP_STAT_NSTATS,
>  };
> @@ -154,7 +158,6 @@ struct mem_cgroup_threshold_ary {
>        struct mem_cgroup_threshold entries[0];
>  };
>
> -static bool mem_cgroup_threshold_check(struct mem_cgroup *mem);
>  static void mem_cgroup_threshold(struct mem_cgroup *mem);
>
>  /*
> @@ -392,19 +395,6 @@ mem_cgroup_remove_exceeded(struct mem_cg
>        spin_unlock(&mctz->lock);
>  }
>
> -static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem)
> -{
> -       bool ret = false;
> -       s64 val;
> -
> -       val = this_cpu_read(mem->stat->count[MEM_CGROUP_STAT_SOFTLIMIT]);
> -       if (unlikely(val < 0)) {
> -               this_cpu_write(mem->stat->count[MEM_CGROUP_STAT_SOFTLIMIT],
> -                               SOFTLIMIT_EVENTS_THRESH);
> -               ret = true;
> -       }
> -       return ret;
> -}
>
>  static void mem_cgroup_update_tree(struct mem_cgroup *mem, struct page *page)
>  {
> @@ -542,8 +532,7 @@ static void mem_cgroup_charge_statistics
>                __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGIN_COUNT]);
>        else
>                __this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_PGPGOUT_COUNT]);
> -       __this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_SOFTLIMIT]);
> -       __this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_THRESHOLDS]);
> +       __this_cpu_inc(mem->stat->count[MEM_CGROUP_EVENTS]);
>
>        preempt_enable();
>  }
> @@ -563,6 +552,29 @@ static unsigned long mem_cgroup_get_loca
>        return total;
>  }
>
> +static bool __memcg_event_check(struct mem_cgroup *mem, int event_mask_shift)

inline?

> +{
> +       s64 val;
> +
> +       val = this_cpu_read(mem->stat->count[MEM_CGROUP_EVENTS]);
> +
> +       return !(val & ((1 << event_mask_shift) - 1));
> +}
> +
> +/*
> + * Check events in order.
> + *
> + */
> +static void memcg_check_events(struct mem_cgroup *mem, struct page *page)

Ditto.

> +{
> +       /* threshold event is triggered in finer grain than soft limit */
> +       if (unlikely(__memcg_event_check(mem, THRESHOLDS_EVENTS_THRESH))) {
> +               mem_cgroup_threshold(mem);
> +               if (unlikely(__memcg_event_check(mem, SOFTLIMIT_EVENTS_THRESH)))
> +                       mem_cgroup_update_tree(mem, page);
> +       }
> +}
> +
>  static struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont)
>  {
>        return container_of(cgroup_subsys_state(cont,
> @@ -1686,11 +1698,7 @@ static void __mem_cgroup_commit_charge(s
>         * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
>         * if they exceeds softlimit.
>         */
> -       if (mem_cgroup_soft_limit_check(mem))
> -               mem_cgroup_update_tree(mem, pc->page);
> -       if (mem_cgroup_threshold_check(mem))
> -               mem_cgroup_threshold(mem);
> -
> +       memcg_check_events(mem, pc->page);
>  }
>
>  /**
> @@ -1760,6 +1768,11 @@ static int mem_cgroup_move_account(struc
>                ret = 0;
>        }
>        unlock_page_cgroup(pc);
> +       /*
> +        * check events
> +        */
> +       memcg_check_events(to, pc->page);
> +       memcg_check_events(from, pc->page);
>        return ret;
>  }
>
> @@ -2128,10 +2141,7 @@ __mem_cgroup_uncharge_common(struct page
>        mz = page_cgroup_zoneinfo(pc);
>        unlock_page_cgroup(pc);
>
> -       if (mem_cgroup_soft_limit_check(mem))
> -               mem_cgroup_update_tree(mem, page);
> -       if (mem_cgroup_threshold_check(mem))
> -               mem_cgroup_threshold(mem);
> +       memcg_check_events(mem, page);
>        /* at swapout, this memcg will be accessed to record to swap */
>        if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
>                css_put(&mem->css);
> @@ -3207,20 +3217,6 @@ static int mem_cgroup_swappiness_write(s
>        return 0;
>  }
>
> -static bool mem_cgroup_threshold_check(struct mem_cgroup *mem)
> -{
> -       bool ret = false;
> -       s64 val;
> -
> -       val = this_cpu_read(mem->stat->count[MEM_CGROUP_STAT_THRESHOLDS]);
> -       if (unlikely(val < 0)) {
> -               this_cpu_write(mem->stat->count[MEM_CGROUP_STAT_THRESHOLDS],
> -                               THRESHOLDS_EVENTS_THRESH);
> -               ret = true;
> -       }
> -       return ret;
> -}
> -
>  static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
>  {
>        struct mem_cgroup_threshold_ary *t;
>
>

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