Re: [patch] mm: memcontrol: inline memcg->move_lock locking

[Michal Hocko]

On Thu 23-10-14 10:33:02, Johannes Weiner wrote:
> The wrappers around taking and dropping the memcg->move_lock spinlock
> add nothing of value.  Inline the spinlock calls into the callsites.
> 
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Acked-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>

Acked-by: Michal Hocko <mhocko@xxxxxxx>

> ---
>  mm/memcontrol.c | 28 ++++++----------------------
>  1 file changed, 6 insertions(+), 22 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 09fece0eb9f1..a5c9aa4688e8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1522,23 +1522,6 @@ static bool mem_cgroup_wait_acct_move(struct mem_cgroup *memcg)
>  	return false;
>  }
>  
> -/*
> - * Take this lock when
> - * - a code tries to modify page's memcg while it's USED.
> - * - a code tries to modify page state accounting in a memcg.
> - */
> -static void move_lock_mem_cgroup(struct mem_cgroup *memcg,
> -				  unsigned long *flags)
> -{
> -	spin_lock_irqsave(&memcg->move_lock, *flags);
> -}
> -
> -static void move_unlock_mem_cgroup(struct mem_cgroup *memcg,
> -				unsigned long *flags)
> -{
> -	spin_unlock_irqrestore(&memcg->move_lock, *flags);
> -}
> -
>  #define K(x) ((x) << (PAGE_SHIFT-10))
>  /**
>   * mem_cgroup_print_oom_info: Print OOM information relevant to memory controller.
> @@ -2156,9 +2139,9 @@ again:
>  	if (atomic_read(&memcg->moving_account) <= 0)
>  		return memcg;
>  
> -	move_lock_mem_cgroup(memcg, flags);
> +	spin_lock_irqsave(&memcg->move_lock, *flags);
>  	if (memcg != pc->mem_cgroup) {
> -		move_unlock_mem_cgroup(memcg, flags);
> +		spin_unlock_irqrestore(&memcg->move_lock, *flags);
>  		goto again;
>  	}
>  	*locked = true;
> @@ -2176,7 +2159,7 @@ void mem_cgroup_end_page_stat(struct mem_cgroup *memcg, bool locked,
>  			      unsigned long flags)
>  {
>  	if (memcg && locked)
> -		move_unlock_mem_cgroup(memcg, &flags);
> +		spin_unlock_irqrestore(&memcg->move_lock, flags);
>  
>  	rcu_read_unlock();
>  }
> @@ -3219,7 +3202,7 @@ static int mem_cgroup_move_account(struct page *page,
>  	if (pc->mem_cgroup != from)
>  		goto out_unlock;
>  
> -	move_lock_mem_cgroup(from, &flags);
> +	spin_lock_irqsave(&from->move_lock, flags);
>  
>  	if (!PageAnon(page) && page_mapped(page)) {
>  		__this_cpu_sub(from->stat->count[MEM_CGROUP_STAT_FILE_MAPPED],
> @@ -3243,7 +3226,8 @@ static int mem_cgroup_move_account(struct page *page,
>  
>  	/* caller should have done css_get */
>  	pc->mem_cgroup = to;
> -	move_unlock_mem_cgroup(from, &flags);
> +	spin_unlock_irqrestore(&from->move_lock, flags);
> +
>  	ret = 0;
>  
>  	local_irq_disable();
> -- 
> 2.1.2
> 

-- 
Michal Hocko
SUSE Labs
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