Re: [RFC][PATCH 02/10] zsmalloc: always keep per-class stats

Minchan Kim
2015-06-04T02:18:33Z

On Sat, May 30, 2015 at 12:05:20AM +0900, Sergey Senozhatsky wrote:
> always account per-class `zs_size_stat' stats. this data will
> help us make better decisions during compaction. we are especially
> interested in OBJ_ALLOCATED and OBJ_USED, which can tell us if
> class compaction will result in any memory gain.
>
> for instance, we know the number of allocated objects in the class,
> the number of objects being used (so we also know how many objects
> are not used) and the number of objects per-page. so we can estimate
> how many pages compaction can free (pages that will turn into
> ZS_EMPTY during compaction).

Fair enough but I need to read further patches to see if we need
really this at the moment.

I hope it would be better to write down more detail in cover-letter
so when I read just [0/0] I realize your goal and approach without
looking into detail in each patch.

>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> ---
> mm/zsmalloc.c | 49 ++++++++++++-------------------------------------
> 1 file changed, 12 insertions(+), 37 deletions(-)
>
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index e615b31..778b8db 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -169,14 +169,12 @@ enum zs_stat_type {
> NR_ZS_STAT_TYPE,
> };
>
> -#ifdef CONFIG_ZSMALLOC_STAT
> -
> -static struct dentry *zs_stat_root;
> -
> struct zs_size_stat {
> unsigned long objs[NR_ZS_STAT_TYPE];
> };
>
> +#ifdef CONFIG_ZSMALLOC_STAT
> +static struct dentry *zs_stat_root;
> #endif
>
> /*
> @@ -201,25 +199,21 @@ static int zs_size_classes;
> static const int fullness_threshold_frac = 4;
>
> struct size_class {
> + spinlock_t lock;
> + struct page *fullness_list[_ZS_NR_FULLNESS_GROUPS];
> /*
> * Size of objects stored in this class. Must be multiple
> * of ZS_ALIGN.
> */
> - int size;
> - unsigned int index;
> + int size;
> + unsigned int index;
>
> /* Number of PAGE_SIZE sized pages to combine to form a 'zspage' */
> - int pages_per_zspage;
> - /* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
> - bool huge;
> -
> -#ifdef CONFIG_ZSMALLOC_STAT
> - struct zs_size_stat stats;
> -#endif
> -
> - spinlock_t lock;
> + int pages_per_zspage;
> + struct zs_size_stat stats;
>
> - struct page *fullness_list[_ZS_NR_FULLNESS_GROUPS];
> + /* huge object: pages_per_zspage == 1 && maxobj_per_zspage == 1 */
> + bool huge;
> };
>
> /*
> @@ -439,8 +433,6 @@ static int get_size_class_index(int size)
> return min(zs_size_classes - 1, idx);
> }
>
> -#ifdef CONFIG_ZSMALLOC_STAT
> -
> static inline void zs_stat_inc(struct size_class *class,
> enum zs_stat_type type, unsigned long cnt)
> {
> @@ -459,6 +451,8 @@ static inline unsigned long zs_stat_get(struct size_class *class,
> return class->stats.objs[type];
> }
>
> +#ifdef CONFIG_ZSMALLOC_STAT
> +
> static int __init zs_stat_init(void)
> {
> if (!debugfs_initialized())
> @@ -574,23 +568,6 @@ static void zs_pool_stat_destroy(struct zs_pool *pool)
> }
>
> #else /* CONFIG_ZSMALLOC_STAT */
> -
> -static inline void zs_stat_inc(struct size_class *class,
> - enum zs_stat_type type, unsigned long cnt)
> -{
> -}
> -
> -static inline void zs_stat_dec(struct size_class *class,
> - enum zs_stat_type type, unsigned long cnt)
> -{
> -}
> -
> -static inline unsigned long zs_stat_get(struct size_class *class,
> - enum zs_stat_type type)
> -{
> - return 0;
> -}
> -
> static int __init zs_stat_init(void)
> {
> return 0;
> @@ -608,7 +585,6 @@ static inline int zs_pool_stat_create(char *name, struct zs_pool *pool)
> static inline void zs_pool_stat_destroy(struct zs_pool *pool)
> {
> }
> -
> #endif
>
>
> @@ -1682,7 +1658,6 @@ static void putback_zspage(struct zs_pool *pool, struct size_class *class,
> class->size, class->pages_per_zspage));
> atomic_long_sub(class->pages_per_zspage,
> &pool->pages_allocated);
> -
> free_zspage(first_page);
> }
> }
> --
> 2.4.2.337.gfae46aa
>

--
Kind regards,
Minchan Kim