Re: [External] Re: [PATCH v3 7/7] mm: memcontrol: make the slab calculation consistent

[Muchun Song <songmuchun@bytedance.com>]

On Tue, Dec 15, 2020 at 9:35 PM Michal Hocko <mhocko@suse.com> wrote:
>
> On Tue 08-12-20 12:18:47, Muchun Song wrote:
> > 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.
>
> This changelog doesn't explain, what is the problem, why do we care and
> why the additional code is worthwile.

Thank you. Will update the commit log for more clear.

>
> > 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;
> > +     }
> > +
> > +     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_page_state_output(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
>
> --
> Michal Hocko
> SUSE Labs



-- 
Yours,
Muchun