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SubjectRe: [RFC][PATCH v3 10/10] memcg : reclaim statistics
From
Hi Kame:

I applied the patch on top of mmotm-2011-05-12-15-52. After boot up, i
keep getting the following crash by reading the
/dev/cgroup/memory/memory.reclaim_stat

[ 200.776366] Kernel panic - not syncing: Fatal exception
[ 200.781591] Pid: 7535, comm: cat Tainted: G D W 2.6.39-mcg-DEV #130
[ 200.788463] Call Trace:
[ 200.790916] [<ffffffff81405a75>] panic+0x91/0x194
[ 200.797096] [<ffffffff81408ac8>] oops_end+0xae/0xbe
[ 200.803450] [<ffffffff810398d3>] die+0x5a/0x63
[ 200.809366] [<ffffffff81408561>] do_trap+0x121/0x130
[ 200.814427] [<ffffffff81037fe6>] do_divide_error+0x90/0x99
[#1] SMP
[ 200.821395] [<ffffffff81112bcb>] ? mem_cgroup_reclaim_stat_read+0x28/0xf0
[ 200.829624] [<ffffffff81104509>] ? page_add_new_anon_rmap+0x7e/0x90
[ 200.837372] [<ffffffff810fb7f8>] ? handle_pte_fault+0x28a/0x775
[ 200.844773] [<ffffffff8140f0f5>] divide_error+0x15/0x20
[ 200.851471] [<ffffffff81112bcb>] ? mem_cgroup_reclaim_stat_read+0x28/0xf0
[ 200.859729] [<ffffffff810a4a01>] cgroup_seqfile_show+0x38/0x46
[ 200.867036] [<ffffffff810a4d72>] ? cgroup_lock+0x17/0x17
[ 200.872444] [<ffffffff81133f2c>] seq_read+0x182/0x361
[ 200.878984] [<ffffffff8111a0c4>] vfs_read+0xab/0x107
[ 200.885403] [<ffffffff8111a1e0>] sys_read+0x4a/0x6e
[ 200.891764] [<ffffffff8140f469>] sysenter_dispatch+0x7/0x27

I will debug it, but like to post here in case i missed some patches in between.

--Ying

On Wed, May 25, 2011 at 10:36 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
> This patch adds a file memory.reclaim_stat.
>
> This file shows following.
> ==
> recent_scan_success_ratio  12 # recent reclaim/scan ratio.
> limit_scan_pages 671          # scan caused by hitting limit.
> limit_freed_pages 538         # freed pages by limit_scan
> limit_elapsed_ns 518555076    # elapsed time in LRU scanning by limit.
> soft_scan_pages 0             # scan caused by softlimit.
> soft_freed_pages 0            # freed pages by soft_scan.
> soft_elapsed_ns 0             # elapsed time in LRU scanning by softlimit.
> margin_scan_pages 16744221    # scan caused by auto-keep-margin
> margin_freed_pages 565943     # freed pages by auto-keep-margin.
> margin_elapsed_ns 5545388791  # elapsed time in LRU scanning by auto-keep-margin
>
> This patch adds a new file rather than adding more stats to memory.stat. By it,
> this support "reset" accounting by
>
>  # echo 0 > .../memory.reclaim_stat
>
> This is good for debug and tuning.
>
> TODO:
>  - add Documentaion.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> ---
>  mm/memcontrol.c |   87 ++++++++++++++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 79 insertions(+), 8 deletions(-)
>
> Index: memcg_async/mm/memcontrol.c
> ===================================================================
> --- memcg_async.orig/mm/memcontrol.c
> +++ memcg_async/mm/memcontrol.c
> @@ -216,6 +216,13 @@ static void mem_cgroup_update_margin_to_
>  static void mem_cgroup_may_async_reclaim(struct mem_cgroup *mem);
>  static void mem_cgroup_reflesh_scan_ratio(struct mem_cgroup *mem);
>
> +enum scan_type {
> +       LIMIT_SCAN,     /* scan memory because memcg hits limit */
> +       SOFT_SCAN,      /* scan memory because of soft limit */
> +       MARGIN_SCAN,    /* scan memory for making margin to limit */
> +       NR_SCAN_TYPES,
> +};
> +
>  /*
>  * The memory controller data structure. The memory controller controls both
>  * page cache and RSS per cgroup. We would eventually like to provide
> @@ -300,6 +307,13 @@ struct mem_cgroup {
>        unsigned long   scanned;
>        unsigned long   reclaimed;
>        unsigned long   next_scanratio_update;
> +       /* For statistics */
> +       struct {
> +               unsigned long nr_scanned_pages;
> +               unsigned long nr_reclaimed_pages;
> +               unsigned long elapsed_ns;
> +       } scan_stat[NR_SCAN_TYPES];
> +
>        /*
>         * percpu counter.
>         */
> @@ -1426,7 +1440,9 @@ unsigned int mem_cgroup_swappiness(struc
>
>  static void __mem_cgroup_update_scan_ratio(struct mem_cgroup *mem,
>                                unsigned long scanned,
> -                               unsigned long reclaimed)
> +                               unsigned long reclaimed,
> +                               unsigned long elapsed,
> +                               enum scan_type type)
>  {
>        unsigned long limit;
>
> @@ -1439,6 +1455,9 @@ static void __mem_cgroup_update_scan_rat
>                mem->scanned /= 2;
>                mem->reclaimed /= 2;
>        }
> +       mem->scan_stat[type].nr_scanned_pages += scanned;
> +       mem->scan_stat[type].nr_reclaimed_pages += reclaimed;
> +       mem->scan_stat[type].elapsed_ns += elapsed;
>        spin_unlock(&mem->scan_stat_lock);
>  }
>
> @@ -1448,6 +1467,8 @@ static void __mem_cgroup_update_scan_rat
>  * @root : root memcg of hierarchy walk.
>  * @scanned : scanned pages
>  * @reclaimed: reclaimed pages.
> + * @elapsed: used time for memory reclaim
> + * @type : scan type as LIMIT_SCAN, SOFT_SCAN, MARGIN_SCAN.
>  *
>  * record scan/reclaim ratio to the memcg both to a child and it's root
>  * mem cgroup, which is a reclaim target. This value is used for
> @@ -1457,11 +1478,14 @@ static void __mem_cgroup_update_scan_rat
>  static void mem_cgroup_update_scan_ratio(struct mem_cgroup *mem,
>                                  struct mem_cgroup *root,
>                                unsigned long scanned,
> -                               unsigned long reclaimed)
> +                               unsigned long reclaimed,
> +                               unsigned long elapsed,
> +                               int type)
>  {
> -       __mem_cgroup_update_scan_ratio(mem, scanned, reclaimed);
> +       __mem_cgroup_update_scan_ratio(mem, scanned, reclaimed, elapsed, type);
>        if (mem != root)
> -               __mem_cgroup_update_scan_ratio(root, scanned, reclaimed);
> +               __mem_cgroup_update_scan_ratio(root, scanned, reclaimed,
> +                                       elapsed, type);
>
>  }
>
> @@ -1906,6 +1930,7 @@ static int mem_cgroup_hierarchical_recla
>        bool is_kswapd = false;
>        unsigned long excess;
>        unsigned long nr_scanned;
> +       unsigned long start, end, elapsed;
>
>        excess = res_counter_soft_limit_excess(&root_mem->res) >> PAGE_SHIFT;
>
> @@ -1947,18 +1972,24 @@ static int mem_cgroup_hierarchical_recla
>                }
>                /* we use swappiness of local cgroup */
>                if (check_soft) {
> +                       start = sched_clock();
>                        ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
>                                noswap, zone, &nr_scanned);
> +                       end = sched_clock();
> +                       elapsed = end - start;
>                        *total_scanned += nr_scanned;
>                        mem_cgroup_soft_steal(victim, is_kswapd, ret);
>                        mem_cgroup_soft_scan(victim, is_kswapd, nr_scanned);
>                        mem_cgroup_update_scan_ratio(victim,
> -                                       root_mem, nr_scanned, ret);
> +                               root_mem, nr_scanned, ret, elapsed, SOFT_SCAN);
>                } else {
> +                       start = sched_clock();
>                        ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
>                                        noswap, &nr_scanned);
> +                       end = sched_clock();
> +                       elapsed = end - start;
>                        mem_cgroup_update_scan_ratio(victim,
> -                                       root_mem, nr_scanned, ret);
> +                               root_mem, nr_scanned, ret, elapsed, LIMIT_SCAN);
>                }
>                css_put(&victim->css);
>                /*
> @@ -4003,7 +4034,7 @@ static void mem_cgroup_async_shrink_work
>        struct delayed_work *dw = to_delayed_work(work);
>        struct mem_cgroup *mem, *victim;
>        long nr_to_reclaim;
> -       unsigned long nr_scanned, nr_reclaimed;
> +       unsigned long nr_scanned, nr_reclaimed, start, end;
>        int delay = 0;
>
>        mem = container_of(dw, struct mem_cgroup, async_work);
> @@ -4022,9 +4053,12 @@ static void mem_cgroup_async_shrink_work
>        if (!victim)
>                goto finish_scan;
>
> +       start = sched_clock();
>        nr_reclaimed = mem_cgroup_shrink_rate_limited(victim, nr_to_reclaim,
>                                        &nr_scanned);
> -       mem_cgroup_update_scan_ratio(victim, mem, nr_scanned, nr_reclaimed);
> +       end = sched_clock();
> +       mem_cgroup_update_scan_ratio(victim, mem, nr_scanned, nr_reclaimed,
> +                       end - start, MARGIN_SCAN);
>        css_put(&victim->css);
>
>        /* If margin is enough big, stop */
> @@ -4680,6 +4714,38 @@ static int mem_control_stat_show(struct
>        return 0;
>  }
>
> +static int mem_cgroup_reclaim_stat_read(struct cgroup *cont, struct cftype *cft,
> +                                struct cgroup_map_cb *cb)
> +{
> +       struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
> +       u64 val;
> +       int i; /* for indexing scan_stat[] */
> +
> +       val = mem->reclaimed * 100 / mem->scanned;
> +       cb->fill(cb, "recent_scan_success_ratio", val);
> +       i  = LIMIT_SCAN;
> +       cb->fill(cb, "limit_scan_pages", mem->scan_stat[i].nr_scanned_pages);
> +       cb->fill(cb, "limit_freed_pages", mem->scan_stat[i].nr_reclaimed_pages);
> +       cb->fill(cb, "limit_elapsed_ns", mem->scan_stat[i].elapsed_ns);
> +       i = SOFT_SCAN;
> +       cb->fill(cb, "soft_scan_pages", mem->scan_stat[i].nr_scanned_pages);
> +       cb->fill(cb, "soft_freed_pages", mem->scan_stat[i].nr_reclaimed_pages);
> +       cb->fill(cb, "soft_elapsed_ns", mem->scan_stat[i].elapsed_ns);
> +       i = MARGIN_SCAN;
> +       cb->fill(cb, "margin_scan_pages", mem->scan_stat[i].nr_scanned_pages);
> +       cb->fill(cb, "margin_freed_pages", mem->scan_stat[i].nr_reclaimed_pages);
> +       cb->fill(cb, "margin_elapsed_ns", mem->scan_stat[i].elapsed_ns);
> +       return 0;
> +}
> +
> +static int mem_cgroup_reclaim_stat_reset(struct cgroup *cgrp, unsigned int event)
> +{
> +       struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
> +       memset(mem->scan_stat, 0, sizeof(mem->scan_stat));
> +       return 0;
> +}
> +
> +
>  /*
>  * User flags for async_control is a subset of mem->async_flags. But
>  * this needs to be defined independently to hide implemation details.
> @@ -5163,6 +5229,11 @@ static struct cftype mem_cgroup_files[]
>                .open = mem_control_numa_stat_open,
>        },
>  #endif
> +       {
> +               .name = "reclaim_stat",
> +               .read_map = mem_cgroup_reclaim_stat_read,
> +               .trigger = mem_cgroup_reclaim_stat_reset,
> +       }
>  };
>
>  #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
>
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