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References: <20201208041847.72122-1-songmuchun@bytedance.com> <20201208041847.72122-8-songmuchun@bytedance.com>
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From:   Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Date:   Tue, 8 Dec 2020 08:20:49 +0100
Message-ID: <CAM9Jb+jg7dD3u4b8P4X_6ginSM3UwVtmbdQzjaencb0r3_bAuQ@mail.gmail.com>
Subject: Re: [PATCH v3 7/7] mm: memcontrol: make the slab calculation consistent
To:     Muchun Song <songmuchun@bytedance.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>, adobriyan@gmail.com,
        Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>, vdavydov.dev@gmail.com,
        Hugh Dickins <hughd@google.com>, shakeelb@google.com,
        guro@fb.com, samitolvanen@google.com, feng.tang@intel.com,
        neilb@suse.de, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-fsdevel@vger.kernel.org, Linux MM <linux-mm@kvack.org>,
        cgroups@vger.kernel.org
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Precedence: bulk

> Although the ratio of the slab is one, we also should read the ratio
> from the related memory_stats instead of hard-coding. And the local
> variable of size is already the value of slab_unreclaimable. So we
> do not need to read again.
>
> We can drop the ratio in struct memory_stat. This can make the code
> clean and simple. And get rid of the awkward mix of static and runtime
> initialization of the memory_stats table.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
>  mm/memcontrol.c | 112 ++++++++++++++++++++++++++++++++++++--------------------
>  1 file changed, 73 insertions(+), 39 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a40797a27f87..841ea37cc123 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1511,49 +1511,78 @@ static bool mem_cgroup_wait_acct_move(struct mem_cgroup *memcg)
>
>  struct memory_stat {
>         const char *name;
> -       unsigned int ratio;
>         unsigned int idx;
>  };
>
>  static const struct memory_stat memory_stats[] = {
> -       { "anon", PAGE_SIZE, NR_ANON_MAPPED },
> -       { "file", PAGE_SIZE, NR_FILE_PAGES },
> -       { "kernel_stack", 1024, NR_KERNEL_STACK_KB },
> -       { "pagetables", PAGE_SIZE, NR_PAGETABLE },
> -       { "percpu", 1, MEMCG_PERCPU_B },
> -       { "sock", PAGE_SIZE, MEMCG_SOCK },
> -       { "shmem", PAGE_SIZE, NR_SHMEM },
> -       { "file_mapped", PAGE_SIZE, NR_FILE_MAPPED },
> -       { "file_dirty", PAGE_SIZE, NR_FILE_DIRTY },
> -       { "file_writeback", PAGE_SIZE, NR_WRITEBACK },
> +       { "anon",                       NR_ANON_MAPPED                  },
> +       { "file",                       NR_FILE_PAGES                   },
> +       { "kernel_stack",               NR_KERNEL_STACK_KB              },
> +       { "pagetables",                 NR_PAGETABLE                    },
> +       { "percpu",                     MEMCG_PERCPU_B                  },
> +       { "sock",                       MEMCG_SOCK                      },
> +       { "shmem",                      NR_SHMEM                        },
> +       { "file_mapped",                NR_FILE_MAPPED                  },
> +       { "file_dirty",                 NR_FILE_DIRTY                   },
> +       { "file_writeback",             NR_WRITEBACK                    },
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> -       { "anon_thp", PAGE_SIZE, NR_ANON_THPS },
> -       { "file_thp", PAGE_SIZE, NR_FILE_THPS },
> -       { "shmem_thp", PAGE_SIZE, NR_SHMEM_THPS },
> +       { "anon_thp",                   NR_ANON_THPS                    },
> +       { "file_thp",                   NR_FILE_THPS                    },
> +       { "shmem_thp",                  NR_SHMEM_THPS                   },
>  #endif
> -       { "inactive_anon", PAGE_SIZE, NR_INACTIVE_ANON },
> -       { "active_anon", PAGE_SIZE, NR_ACTIVE_ANON },
> -       { "inactive_file", PAGE_SIZE, NR_INACTIVE_FILE },
> -       { "active_file", PAGE_SIZE, NR_ACTIVE_FILE },
> -       { "unevictable", PAGE_SIZE, NR_UNEVICTABLE },
> -
> -       /*
> -        * Note: The slab_reclaimable and slab_unreclaimable must be
> -        * together and slab_reclaimable must be in front.
> -        */
> -       { "slab_reclaimable", 1, NR_SLAB_RECLAIMABLE_B },
> -       { "slab_unreclaimable", 1, NR_SLAB_UNRECLAIMABLE_B },
> +       { "inactive_anon",              NR_INACTIVE_ANON                },
> +       { "active_anon",                NR_ACTIVE_ANON                  },
> +       { "inactive_file",              NR_INACTIVE_FILE                },
> +       { "active_file",                NR_ACTIVE_FILE                  },
> +       { "unevictable",                NR_UNEVICTABLE                  },
> +       { "slab_reclaimable",           NR_SLAB_RECLAIMABLE_B           },
> +       { "slab_unreclaimable",         NR_SLAB_UNRECLAIMABLE_B         },
>
>         /* The memory events */
> -       { "workingset_refault_anon", 1, WORKINGSET_REFAULT_ANON },
> -       { "workingset_refault_file", 1, WORKINGSET_REFAULT_FILE },
> -       { "workingset_activate_anon", 1, WORKINGSET_ACTIVATE_ANON },
> -       { "workingset_activate_file", 1, WORKINGSET_ACTIVATE_FILE },
> -       { "workingset_restore_anon", 1, WORKINGSET_RESTORE_ANON },
> -       { "workingset_restore_file", 1, WORKINGSET_RESTORE_FILE },
> -       { "workingset_nodereclaim", 1, WORKINGSET_NODERECLAIM },
> +       { "workingset_refault_anon",    WORKINGSET_REFAULT_ANON         },
> +       { "workingset_refault_file",    WORKINGSET_REFAULT_FILE         },
> +       { "workingset_activate_anon",   WORKINGSET_ACTIVATE_ANON        },
> +       { "workingset_activate_file",   WORKINGSET_ACTIVATE_FILE        },
> +       { "workingset_restore_anon",    WORKINGSET_RESTORE_ANON         },
> +       { "workingset_restore_file",    WORKINGSET_RESTORE_FILE         },
> +       { "workingset_nodereclaim",     WORKINGSET_NODERECLAIM          },
>  };
>
> +/* Translate stat items to the correct unit for memory.stat output */
> +static int memcg_page_state_unit(int item)
> +{
> +       int unit;
> +
> +       switch (item) {
> +       case MEMCG_PERCPU_B:
> +       case NR_SLAB_RECLAIMABLE_B:
> +       case NR_SLAB_UNRECLAIMABLE_B:
> +       case WORKINGSET_REFAULT_ANON:
> +       case WORKINGSET_REFAULT_FILE:
> +       case WORKINGSET_ACTIVATE_ANON:
> +       case WORKINGSET_ACTIVATE_FILE:
> +       case WORKINGSET_RESTORE_ANON:
> +       case WORKINGSET_RESTORE_FILE:
> +       case WORKINGSET_NODERECLAIM:
> +               unit = 1;
> +               break;
> +       case NR_KERNEL_STACK_KB:
> +               unit = SZ_1K;
> +               break;
> +       default:
> +               unit = PAGE_SIZE;
> +               break;
 break not needed here, or maybe we can return for every case,
that will avoid "unit" variable.

> +       }
> +
> +       return unit;
> +}
> +
> +static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg,
> +                                                   int item)
> +{
> +       return memcg_page_state(memcg, item) * memcg_page_state_unit(item);
> +}
> +
>  static char *memory_stat_format(struct mem_cgroup *memcg)
>  {
>         struct seq_buf s;
> @@ -1577,13 +1606,12 @@ static char *memory_stat_format(struct mem_cgroup *memcg)
>         for (i = 0; i < ARRAY_SIZE(memory_stats); i++) {
>                 u64 size;
>
> -               size = memcg_page_state(memcg, memory_stats[i].idx);
> -               size *= memory_stats[i].ratio;
> +               size = memcg_page_state_output(memcg, memory_stats[i].idx);
>                 seq_buf_printf(&s, "%s %llu\n", memory_stats[i].name, size);
>
>                 if (unlikely(memory_stats[i].idx == NR_SLAB_UNRECLAIMABLE_B)) {
> -                       size = memcg_page_state(memcg, NR_SLAB_RECLAIMABLE_B) +
> -                              memcg_page_state(memcg, NR_SLAB_UNRECLAIMABLE_B);
> +                       size +=
(memcg,
> +                                                       NR_SLAB_RECLAIMABLE_B);
>                         seq_buf_printf(&s, "slab %llu\n", size);
>                 }
>         }
> @@ -6377,6 +6405,12 @@ static int memory_stat_show(struct seq_file *m, void *v)
>  }
>
>  #ifdef CONFIG_NUMA
> +static inline unsigned long lruvec_page_state_output(struct lruvec *lruvec,
> +                                                    int item)
> +{
> +       return lruvec_page_state(lruvec, item) * memcg_page_state_unit(item);
> +}
> +
>  static int memory_numa_stat_show(struct seq_file *m, void *v)
>  {
>         int i;
> @@ -6394,8 +6428,8 @@ static int memory_numa_stat_show(struct seq_file *m, void *v)
>                         struct lruvec *lruvec;
>
>                         lruvec = mem_cgroup_lruvec(memcg, NODE_DATA(nid));
> -                       size = lruvec_page_state(lruvec, memory_stats[i].idx);
> -                       size *= memory_stats[i].ratio;
> +                       size = lruvec_page_state_output(lruvec,
> +                                                       memory_stats[i].idx);
>                         seq_printf(m, " N%d=%llu", nid, size);
>                 }
>                 seq_putc(m, '\n');
> --
> 2.11.0
>
>