Re: [PATCH] memcg: fix behavior of mem_cgroup_resize_limit()

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Fri, 22 Jul 2011 11:17:03 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> commit:22a668d7 introduced "memsw_is_minimum" flag, which becomes true when
> mem_limit == memsw_limit. The flag is checked at the beginning of reclaim,
> and "noswap" is set if the flag is true, because using swap is meaningless
> in this case.
> 
> This works well in most cases, but when we try to shrink mem_limit, which
> is the same as memsw_limit now, we might fail to shrink mem_limit because
> swap doesn't used.
> 
> This patch fixes this behavior by:
> - check MEM_CGROUP_RECLAIM_SHRINK at the begining of reclaim
> - If it is set, don't set "noswap" flag even if memsw_is_minimum is true.
> 
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>

nice catch.

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

> ---
>  mm/memcontrol.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index ce0d617..cf6bae8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1649,7 +1649,7 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
>  	excess = res_counter_soft_limit_excess(&root_mem->res) >> PAGE_SHIFT;
>  
>  	/* If memsw_is_minimum==1, swap-out is of-no-use. */
> -	if (!check_soft && root_mem->memsw_is_minimum)
> +	if (!check_soft && !shrink && root_mem->memsw_is_minimum)
>  		noswap = true;
>  
>  	while (1) {
> -- 
> 1.7.1
> 
> 

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