Re: [trivial PATCH] Remove pointless next_mz nullification in mem_cgroup_soft_limit_reclaim

[Zhu Yanhai <zhu.yanhai@xxxxxxxxx>]

Michal,
IIUC it's to prevent the infinite loop, as in the end of the do-while
there's
if (!nr_reclaimed &&
    (next_mz == NULL ||
    loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS))
		break;
so the loop will break earlier if all groups are iterated once and no
pages are freed.

Thanks,
Zhu Yanhai

2011/3/29 Michal Hocko <mhocko@xxxxxxx>:
> Hi,
> while reading the code I have encountered the following thing. It is no
> biggie but...
> ---
> From: Michal Hocko <mhocko@xxxxxxx>
> Subject: Remove pointless next_mz nullification in mem_cgroup_soft_limit_reclaim
>
> next_mz is assigned to NULL if __mem_cgroup_largest_soft_limit_node selects
> the same mz. This doesn't make much sense as we assign to the variable
> right in the next loop.
>
> Compiler will probably optimize this out but it is little bit confusing for
> the code reading.
>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
>
> Index: linux-2.6.38-rc8/mm/memcontrol.c
> ===================================================================
> --- linux-2.6.38-rc8.orig/mm/memcontrol.c    2011-03-28 11:25:14.000000000 +0200
> +++ linux-2.6.38-rc8/mm/memcontrol.c  Â2011-03-29 15:24:08.000000000 +0200
> @@ -3349,7 +3349,6 @@ unsigned long mem_cgroup_soft_limit_recl
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â__mem_cgroup_largest_soft_limit_node(mctz);
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Âif (next_mz == mz) {
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Âcss_put(&next_mz->mem->css);
> - Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â next_mz = NULL;
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â} else /* next_mz == NULL or other memcg */
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Âbreak;
> Â Â Â Â Â Â Â Â Â Â Â Â} while (1);
> --
> Michal Hocko
> SUSE Labs
> SUSE LINUX s.r.o.
> Lihovarska 1060/12
> 190 00 Praha 9
> Czech Republic
>
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