Re: [PATCH 4/4] memcg: reduce function dereference

[Michal Hocko <mhocko@suse.cz>]

On Wed 31-07-13 15:31:25, Qiang Huang wrote:
> This function dereferences res far too often, so optimize it.
> 
> Signed-off-by: Sha Zhengju <handai.szj@taobao.com>
> Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>

Reviewed-by: Michal Hocko <mhocko@suse.cz>

> ---
>  kernel/res_counter.c | 19 +++++++++++--------
>  1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/res_counter.c b/kernel/res_counter.c
> index 085d3ae..4aa8a30 100644
> --- a/kernel/res_counter.c
> +++ b/kernel/res_counter.c
> @@ -178,27 +178,30 @@ u64 res_counter_read_u64(struct res_counter *counter, int member)
>  #endif
>  
>  int res_counter_memparse_write_strategy(const char *buf,
> -					unsigned long long *res)
> +					unsigned long long *resp)
>  {
>  	char *end;
> +	unsigned long long res;
>  
>  	/* return RES_COUNTER_MAX(unlimited) if "-1" is specified */
>  	if (*buf == '-') {
> -		*res = simple_strtoull(buf + 1, &end, 10);
> -		if (*res != 1 || *end != '\0')
> +		res = simple_strtoull(buf + 1, &end, 10);
> +		if (res != 1 || *end != '\0')
>  			return -EINVAL;
> -		*res = RES_COUNTER_MAX;
> +		*resp = RES_COUNTER_MAX;
>  		return 0;
>  	}
>  
> -	*res = memparse(buf, &end);
> +	res = memparse(buf, &end);
>  	if (*end != '\0')
>  		return -EINVAL;
>  
> -	if (PAGE_ALIGN(*res) >= *res)
> -		*res = PAGE_ALIGN(*res);
> +	if (PAGE_ALIGN(res) >= res)
> +		res = PAGE_ALIGN(res);
>  	else
> -		*res = RES_COUNTER_MAX;
> +		res = RES_COUNTER_MAX;
> +
> +	*resp = res;
>  
>  	return 0;
>  }
> -- 
> 1.8.3
> 
> 

-- 
Michal Hocko
SUSE Labs

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