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SubjectRe: [PATCH RESEND] mm/vmscan : use vmcan_swappiness( ) basing on MEMCG config to elimiate unnecessary runtime cost
Please fix a typo in subject line (which affects how easy we can access
paticular patches later with grepping subject lines.)

Reviewed-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>

On Mon, Aug 26, 2013 at 09:36:58PM +0800, larmbr wrote:
> Currently, we get the vm_swappiness via vmscan_swappiness(), which
> calls global_reclaim() to check if this is a global reclaim.
>
> Besides, the current implementation of global_reclaim() always returns
> true for the !CONFIG_MEGCG case, and judges the other case by checking
> whether scan_control->target_mem_cgroup is null or not.
>
> Thus, we could just use two versions of vmscan_swappiness() based on
> MEMCG Kconfig , to eliminate the unnecessary run-time cost for
> the !CONFIG_MEMCG at all, and to squash all memcg-related checking
> into the CONFIG_MEMCG version.
>
> Signed-off-by: Zhan Jianyu <nasa4836@gmail.com>
> ---
> mm/memcontrol.c | 6 +++++-
> mm/vmscan.c | 9 +++++++--
> 2 files changed, 12 insertions(+), 3 deletions(-)
>
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index c5792a5..1290320 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1525,9 +1525,13 @@ static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
>
> int mem_cgroup_swappiness(struct mem_cgroup *memcg)
> {
> - struct cgroup *cgrp = memcg->css.cgroup;
> + struct cgroup *cgrp;
> +
> + if (!memcg)
> + return vm_swappiness;
>
> /* root ? */
> + cgrp = memcg->css.cgroup;
> if (cgrp->parent == NULL)
> return vm_swappiness;
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 2cff0d4..1de652d 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1742,12 +1742,17 @@ static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
> return shrink_inactive_list(nr_to_scan, lruvec, sc, lru);
> }
>
> +#ifdef CONFIG_MEMCG
> static int vmscan_swappiness(struct scan_control *sc)
> {
> - if (global_reclaim(sc))
> - return vm_swappiness;
> return mem_cgroup_swappiness(sc->target_mem_cgroup);
> }
> +#else
> +static int vmscan_swappiness(struct scan_control *sc)
> +{
> + return vm_swappiness;
> +}
> +#endif
>
> enum scan_balance {
> SCAN_EQUAL,
>
> --
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