Re: [PATCH v2 19/47] mm: thp: dynamically allocate the thp-related shrinkers

[Muchun Song <muchun.song@xxxxxxxxx>]

On 2023/7/24 17:43, Qi Zheng wrote:
> Use new APIs to dynamically allocate the thp-zero and thp-deferred_split
> shrinkers.
>
> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
> ---
>   mm/huge_memory.c | 69 +++++++++++++++++++++++++++++++-----------------
>   1 file changed, 45 insertions(+), 24 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 8c94b34024a2..4db5a1834d81 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -65,7 +65,11 @@ unsigned long transparent_hugepage_flags __read_mostly =
>         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)|
>         (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG);
>   
> -static struct shrinker deferred_split_shrinker;
> +static struct shrinker *deferred_split_shrinker;
> +static unsigned long deferred_split_count(struct shrinker *shrink,
> +                                         struct shrink_control *sc);
> +static unsigned long deferred_split_scan(struct shrinker *shrink,
> +                                        struct shrink_control *sc);
>   
>   static atomic_t huge_zero_refcount;
>   struct page *huge_zero_page __read_mostly;
> @@ -229,11 +233,7 @@ static unsigned long shrink_huge_zero_page_scan(struct 
> shrinker *shrink,
>         return 0;
>   }
>   
> -static struct shrinker huge_zero_page_shrinker = {
> -       .count_objects = shrink_huge_zero_page_count,
> -       .scan_objects = shrink_huge_zero_page_scan,
> -       .seeks = DEFAULT_SEEKS,
> -};
> +static struct shrinker *huge_zero_page_shrinker;
Same as patch #17.

>   
>   #ifdef CONFIG_SYSFS
>   static ssize_t enabled_show(struct kobject *kobj,
> @@ -454,6 +454,40 @@ static inline void hugepage_exit_sysfs(struct kobject 
> *hugepage_kobj)
>   }
>   #endif /* CONFIG_SYSFS */
>   
> +static int thp_shrinker_init(void)
Better to declare it as __init.

> +{
> +       huge_zero_page_shrinker = shrinker_alloc(0, "thp-zero");
> +       if (!huge_zero_page_shrinker)
> +               return -ENOMEM;
> +
> +       deferred_split_shrinker = shrinker_alloc(SHRINKER_NUMA_AWARE |
> +                                                SHRINKER_MEMCG_AWARE |
> +                                                SHRINKER_NONSLAB,
> +                                                "thp-deferred_split");
> +       if (!deferred_split_shrinker) {
> +               shrinker_free_non_registered(huge_zero_page_shrinker);
> +               return -ENOMEM;
> +       }
> +
> +       huge_zero_page_shrinker->count_objects = shrink_huge_zero_page_count;
> +       huge_zero_page_shrinker->scan_objects = shrink_huge_zero_page_scan;
> +       huge_zero_page_shrinker->seeks = DEFAULT_SEEKS;
> +       shrinker_register(huge_zero_page_shrinker);
> +
> +       deferred_split_shrinker->count_objects = deferred_split_count;
> +       deferred_split_shrinker->scan_objects = deferred_split_scan;
> +       deferred_split_shrinker->seeks = DEFAULT_SEEKS;
> +       shrinker_register(deferred_split_shrinker);
> +
> +       return 0;
> +}
> +
> +static void thp_shrinker_exit(void)
Same as here.

> +{
> +       shrinker_unregister(huge_zero_page_shrinker);
> +       shrinker_unregister(deferred_split_shrinker);
> +}
> +
>   static int __init hugepage_init(void)
>   {
>         int err;
> @@ -482,12 +516,9 @@ static int __init hugepage_init(void)
>         if (err)
>                 goto err_slab;
>   
> -	err = register_shrinker(&huge_zero_page_shrinker, "thp-zero");
> -       if (err)
> -               goto err_hzp_shrinker;
> -       err = register_shrinker(&deferred_split_shrinker, "thp-deferred_split");
> +       err = thp_shrinker_init();
>         if (err)
> -               goto err_split_shrinker;
> +               goto err_shrinker;
>   
>   	/*
>          * By default disable transparent hugepages on smaller systems,
> @@ -505,10 +536,8 @@ static int __init hugepage_init(void)
>   
>   	return 0;
>   err_khugepaged:
> -       unregister_shrinker(&deferred_split_shrinker);
> -err_split_shrinker:
> -       unregister_shrinker(&huge_zero_page_shrinker);
> -err_hzp_shrinker:
> +       thp_shrinker_exit();
> +err_shrinker:
>         khugepaged_destroy();
>   err_slab:
>         hugepage_exit_sysfs(hugepage_kobj);
> @@ -2851,7 +2880,7 @@ void deferred_split_folio(struct folio *folio)
>   #ifdef CONFIG_MEMCG
>                 if (memcg)
>                         set_shrinker_bit(memcg, folio_nid(folio),
> -                                        deferred_split_shrinker.id);
> +                                        deferred_split_shrinker->id);
>   #endif
>         }
>         spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags);
> @@ -2925,14 +2954,6 @@ static unsigned long deferred_split_scan(struct shrinker 
> *shrink,
>         return split;
>   }
>   
> -static struct shrinker deferred_split_shrinker = {
> -       .count_objects = deferred_split_count,
> -       .scan_objects = deferred_split_scan,
> -       .seeks = DEFAULT_SEEKS,
> -       .flags = SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE |
> -                SHRINKER_NONSLAB,
> -};
> -
>   #ifdef CONFIG_DEBUG_FS
>   static void split_huge_pages_all(void)
>   {