[Cc linux-api]
On Mon 17-06-19 10:21:49, Waiman Long wrote:
> There are concerns about memory leaks from extensive use of memory
> cgroups as each memory cgroup creates its own set of kmem caches. There
> is a possiblity that the memcg kmem caches may remain even after the
> memory cgroup removal.
>
> Therefore, it will be useful to show how many memcg caches are present
> for each of the kmem caches.
How is a user going to use that information? Btw. Don't we have an
interface to display the number of (dead) cgroups?
Keeping the rest of the email for the reference.
> As slabinfo reporting code has to iterate
> through all the memcg caches to get the final numbers anyway, there is
> no additional cost in reporting the number of memcg caches available.
>
> The slabinfo version is bumped up to 2.2 as a new "<num_caches>" column
> is added at the end.
>
> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> ---
> mm/slab_common.c | 24 ++++++++++++++++--------
> 1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 58251ba63e4a..c7aa47a99b2b 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1308,13 +1308,13 @@ static void print_slabinfo_header(struct seq_file *m)
> * without _too_ many complaints.
> */
> #ifdef CONFIG_DEBUG_SLAB
> - seq_puts(m, "slabinfo - version: 2.1 (statistics)\n");
> + seq_puts(m, "slabinfo - version: 2.2 (statistics)\n");
> #else
> - seq_puts(m, "slabinfo - version: 2.1\n");
> + seq_puts(m, "slabinfo - version: 2.2\n");
> #endif
> seq_puts(m, "# name <active_objs> <num_objs> <objsize> <objperslab> <pagesperslab>");
> seq_puts(m, " : tunables <limit> <batchcount> <sharedfactor>");
> - seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail>");
> + seq_puts(m, " : slabdata <active_slabs> <num_slabs> <sharedavail> <num_caches>");
> #ifdef CONFIG_DEBUG_SLAB
> seq_puts(m, " : globalstat <listallocs> <maxobjs> <grown> <reaped> <error> <maxfreeable> <nodeallocs> <remotefrees> <alienoverflow>");
> seq_puts(m, " : cpustat <allochit> <allocmiss> <freehit> <freemiss>");
> @@ -1338,14 +1338,18 @@ void slab_stop(struct seq_file *m, void *p)
> mutex_unlock(&slab_mutex);
> }
>
> -static void
> +/*
> + * Return number of memcg caches.
> + */
> +static unsigned int
> memcg_accumulate_slabinfo(struct kmem_cache *s, struct slabinfo *info)
> {
> struct kmem_cache *c;
> struct slabinfo sinfo;
> + unsigned int cnt = 0;
>
> if (!is_root_cache(s))
> - return;
> + return 0;
>
> for_each_memcg_cache(c, s) {
> memset(&sinfo, 0, sizeof(sinfo));
> @@ -1356,17 +1360,20 @@ memcg_accumulate_slabinfo(struct kmem_cache *s, struct slabinfo *info)
> info->shared_avail += sinfo.shared_avail;
> info->active_objs += sinfo.active_objs;
> info->num_objs += sinfo.num_objs;
> + cnt++;
> }
> + return cnt;
> }
>
> static void cache_show(struct kmem_cache *s, struct seq_file *m)
> {
> struct slabinfo sinfo;
> + unsigned int nr_memcg_caches;
>
> memset(&sinfo, 0, sizeof(sinfo));
> get_slabinfo(s, &sinfo);
>
> - memcg_accumulate_slabinfo(s, &sinfo);
> + nr_memcg_caches = memcg_accumulate_slabinfo(s, &sinfo);
>
> seq_printf(m, "%-17s %6lu %6lu %6u %4u %4d",
> cache_name(s), sinfo.active_objs, sinfo.num_objs, s->size,
> @@ -1374,8 +1381,9 @@ static void cache_show(struct kmem_cache *s, struct seq_file *m)
>
> seq_printf(m, " : tunables %4u %4u %4u",
> sinfo.limit, sinfo.batchcount, sinfo.shared);
> - seq_printf(m, " : slabdata %6lu %6lu %6lu",
> - sinfo.active_slabs, sinfo.num_slabs, sinfo.shared_avail);
> + seq_printf(m, " : slabdata %6lu %6lu %6lu %3u",
> + sinfo.active_slabs, sinfo.num_slabs, sinfo.shared_avail,
> + nr_memcg_caches);
> slabinfo_show_stats(m, s);
> seq_putc(m, '\n');
> }
> --
> 2.18.1
--
Michal Hocko
SUSE Labs
