Re: [PATCH] Cgroup: Fix memory accounting scalability in shrink_page_list

[Michal Hocko <mhocko@suse.cz>]

On Thu 19-07-12 16:34:26, Tim Chen wrote:
[...]
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 33dc256..aac5672 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -779,6 +779,7 @@ static unsigned long shrink_page_list(struct list_head *page_list,
>  
>  	cond_resched();
>  
> +	mem_cgroup_uncharge_start();
>  	while (!list_empty(page_list)) {
>  		enum page_references references;
>  		struct address_space *mapping;

Is this safe? We have a scheduling point few lines below. What prevents
from task move while we are in the middle of the batch?

> @@ -1026,6 +1027,7 @@ keep_lumpy:
>  
>  	list_splice(&ret_pages, page_list);
>  	count_vm_events(PGACTIVATE, pgactivate);
> +	mem_cgroup_uncharge_end();
>  	*ret_nr_dirty += nr_dirty;
>  	*ret_nr_writeback += nr_writeback;
>  	return nr_reclaimed;
> 
> 
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-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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