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

Michal Hocko
2013-07-31T08:20:29Z

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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