On Sun 02-02-14 20:33:46, Vladimir Davydov wrote:
> Per-memcg kmem caches are named as follows:
>
> <global-cache-name>(<cgroup-kmem-id>:<cgroup-name>)
>
> where <cgroup-kmem-id> is the unique id of the memcg the cache belongs
> to, <cgroup-name> is the relative name of the memcg on the cgroup fs.
> Cache names are exposed to userspace for debugging purposes (e.g. via
> sysfs in case of slub or via dmesg).
If this is only for debugging purposes then it shouldn't pollute regular
memcg cgroupfs namespace.
> Using relative names makes it impossible in general (in case the cgroup
> hierarchy is not flat) to find out which memcg a particular cache
> belongs to, because <cgroup-kmem-id> is not known to the user. Since
> using absolute cgroup names would be an overkill,
I do not consider it an overkill. We are using the full path when
dumping OOM information so I do not see any reason this should be any
different.
> let's fix this by
> exporting the id of kmem-active memcg via cgroup fs file
> "memory.kmem.id".
>
> Signed-off-by: Vladimir Davydov <vdavy...@parallels.com>
Nacked-by: Michal Hocko <mho...@suse.cz>
> ---
> mm/memcontrol.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 53385cd4e6f0..91d242707404 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -3113,6 +3113,14 @@ int memcg_cache_id(struct mem_cgroup *memcg)
> return memcg ? memcg->kmemcg_id : -1;
> }
>
> +static s64 mem_cgroup_cache_id_read(struct cgroup_subsys_state *css,
> + struct cftype *cft)
> +{
> + struct mem_cgroup *memcg = mem_cgroup_from_css(css);
> +
> + return memcg_can_account_kmem(memcg) ? memcg_cache_id(memcg) : -1;
> +}
> +
> static size_t memcg_caches_array_size(int num_groups)
> {
> ssize_t size;
> @@ -6301,6 +6309,10 @@ static struct cftype mem_cgroup_files[] = {
> #endif
> #ifdef CONFIG_MEMCG_KMEM
> {
> + .name = "kmem.id",
> + .read_s64 = mem_cgroup_cache_id_read,
> + },
> + {
> .name = "kmem.limit_in_bytes",
> .private = MEMFILE_PRIVATE(_KMEM, RES_LIMIT),
> .write_string = mem_cgroup_write,
> --
> 1.7.10.4
>
--
Michal Hocko
SUSE Labs
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