Re: [PATCH 3/5] memcg: lru_size instead of MEM_CGROUP_ZSTAT

[Michal Hocko <mhocko@suse.cz>]

On Sat 31-12-11 23:30:38, Hugh Dickins wrote:
> I never understood why we need a MEM_CGROUP_ZSTAT(mz, idx) macro
> to obscure the LRU counts.  For easier searching?  So call it
> lru_size rather than bare count (lru_length sounds better, but
> would be wrong, since each huge page raises lru_size hugely).

lru_size is unique at the global scope at the moment but this might
change in the future. MEM_CGROUP_ZSTAT should be unique and so easier
to grep or cscope. 
On the other hand lru_size sounds like a better name so I am all for
renaming but we should make sure that we somehow get memcg into it
(either to macro MEM_CGROUP_LRU_SIZE or get rid of macro and have
memcg_lru_size field name - which is ugly long).

> 
> Signed-off-by: Hugh Dickins <hughd@google.com>
> ---
>  mm/memcontrol.c |   14 ++++++--------
>  1 file changed, 6 insertions(+), 8 deletions(-)
> 
> --- mmotm.orig/mm/memcontrol.c	2011-12-30 21:22:05.679339324 -0800
> +++ mmotm/mm/memcontrol.c	2011-12-30 21:23:28.243341326 -0800
> @@ -135,7 +135,7 @@ struct mem_cgroup_reclaim_iter {
>   */
>  struct mem_cgroup_per_zone {
>  	struct lruvec		lruvec;
> -	unsigned long		count[NR_LRU_LISTS];
> +	unsigned long		lru_size[NR_LRU_LISTS];
>  
>  	struct mem_cgroup_reclaim_iter reclaim_iter[DEF_PRIORITY + 1];
>  
> @@ -147,8 +147,6 @@ struct mem_cgroup_per_zone {
>  	struct mem_cgroup	*memcg;		/* Back pointer, we cannot */
>  						/* use container_of	   */
>  };
> -/* Macro for accessing counter */
> -#define MEM_CGROUP_ZSTAT(mz, idx)	((mz)->count[(idx)])
>  
>  struct mem_cgroup_per_node {
>  	struct mem_cgroup_per_zone zoneinfo[MAX_NR_ZONES];
> @@ -713,7 +711,7 @@ mem_cgroup_zone_nr_lru_pages(struct mem_
>  
>  	for_each_lru(l) {
>  		if (BIT(l) & lru_mask)
> -			ret += MEM_CGROUP_ZSTAT(mz, l);
> +			ret += mz->lru_size[l];
>  	}
>  	return ret;
>  }
> @@ -1048,7 +1046,7 @@ struct lruvec *mem_cgroup_lru_add_list(s
>  	memcg = pc->mem_cgroup;
>  	mz = page_cgroup_zoneinfo(memcg, page);
>  	/* compound_order() is stabilized through lru_lock */
> -	MEM_CGROUP_ZSTAT(mz, lru) += 1 << compound_order(page);
> +	mz->lru_size[lru] += 1 << compound_order(page);
>  	return &mz->lruvec;
>  }
>  
> @@ -1076,8 +1074,8 @@ void mem_cgroup_lru_del_list(struct page
>  	VM_BUG_ON(!memcg);
>  	mz = page_cgroup_zoneinfo(memcg, page);
>  	/* huge page split is done under lru_lock. so, we have no races. */
> -	VM_BUG_ON(MEM_CGROUP_ZSTAT(mz, lru) < (1 << compound_order(page)));
> -	MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
> +	VM_BUG_ON(mz->lru_size[lru] < (1 << compound_order(page)));
> +	mz->lru_size[lru] -= 1 << compound_order(page);
>  }
>  
>  void mem_cgroup_lru_del(struct page *page)
> @@ -3615,7 +3613,7 @@ static int mem_cgroup_force_empty_list(s
>  	mz = mem_cgroup_zoneinfo(memcg, node, zid);
>  	list = &mz->lruvec.lists[lru];
>  
> -	loop = MEM_CGROUP_ZSTAT(mz, lru);
> +	loop = mz->lru_size[lru];
>  	/* give some margin against EBUSY etc...*/
>  	loop += 256;
>  	busy = NULL;

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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