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

Sergey Senozhatsky
2015-06-04T02:34:06Z

On (06/04/15 11:18), Minchan Kim wrote:
> 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.
>

sure, will do later today.
I caught a cold, so I'm a bit slow.

-ss

> >
> > 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
>