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SubjectRe: [mm] [PATCH 4/4] Memory cgroup hierarchy feature selector
On Sun, 02 Nov 2008 00:19:02 +0530
Balbir Singh <balbir@linux.vnet.ibm.com> wrote:

>
> Don't enable multiple hierarchy support by default. This patch introduces
> a features element that can be set to enable the nested depth hierarchy
> feature. This feature can only be enabled when there is just one cgroup
> (the root cgroup).
>
Why the flag is for the whole system ?
flag-per-subtree is of no use ?

Thanks,
-Kame

> Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
> ---
>
> mm/memcontrol.c | 38 +++++++++++++++++++++++++++++++++++++-
> 1 file changed, 37 insertions(+), 1 deletion(-)
>
> diff -puN mm/memcontrol.c~memcg-add-hierarchy-selector mm/memcontrol.c
> --- linux-2.6.28-rc2/mm/memcontrol.c~memcg-add-hierarchy-selector 2008-11-02 00:15:00.000000000 +0530
> +++ linux-2.6.28-rc2-balbir/mm/memcontrol.c 2008-11-02 00:15:00.000000000 +0530
> @@ -40,6 +40,9 @@
> struct cgroup_subsys mem_cgroup_subsys __read_mostly;
> #define MEM_CGROUP_RECLAIM_RETRIES 5
>
> +static unsigned long mem_cgroup_features;
> +#define MEM_CGROUP_FEAT_HIERARCHY 0x1
> +
> /*
> * Statistics for memory cgroup.
> */
> @@ -1080,6 +1083,31 @@ out:
> return ret;
> }
>
> +static u64 mem_cgroup_feature_read(struct cgroup *cont, struct cftype *cft)
> +{
> + return mem_cgroup_features;
> +}
> +
> +static int mem_cgroup_feature_write(struct cgroup *cont, struct cftype *cft,
> + u64 val)
> +{
> + int retval = 0;
> + struct cgroup *cgroup = init_mem_cgroup.css.cgroup;
> +
> + if (val & MEM_CGROUP_FEAT_HIERARCHY) {
> + if (list_empty(&cgroup->children))
> + mem_cgroup_features |= MEM_CGROUP_FEAT_HIERARCHY;
> + else
> + retval = -EBUSY;
> + } else {
> + if (list_empty(&cgroup->children))
> + mem_cgroup_features &= ~MEM_CGROUP_FEAT_HIERARCHY;
> + else
> + retval = -EBUSY;
> + }
> + return retval;
> +}
> +
> static u64 mem_cgroup_read(struct cgroup *cont, struct cftype *cft)
> {
> return res_counter_read_u64(&mem_cgroup_from_cont(cont)->res,
> @@ -1214,6 +1242,11 @@ static struct cftype mem_cgroup_files[]
> .name = "stat",
> .read_map = mem_control_stat_show,
> },
> + {
> + .name = "features",
> + .write_u64 = mem_cgroup_feature_write,
> + .read_u64 = mem_cgroup_feature_read,
> + },
> };
>
> static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
> @@ -1292,7 +1325,10 @@ mem_cgroup_create(struct cgroup_subsys *
> return ERR_PTR(-ENOMEM);
> }
>
> - res_counter_init(&mem->res, parent ? &parent->res : NULL);
> + if ((mem_cgroup_features & MEM_CGROUP_FEAT_HIERARCHY) && parent)
> + res_counter_init(&mem->res, &parent->res);
> + else
> + res_counter_init(&mem->res, NULL);
>
> for_each_node_state(node, N_POSSIBLE)
> if (alloc_mem_cgroup_per_zone_info(mem, node))
> _
>
> --
> Balbir
>



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