On Fri, Jan 28, 2022 at 02:56:42PM -0500, Waiman Long wrote:
> It was found that a number of offlined memcgs were not freed because
> they were pinned by some charged pages that were present. Even "echo
> 1 > /proc/sys/vm/drop_caches" wasn't able to free those pages. These
> offlined but not freed memcgs tend to increase in number over time with
> the side effect that percpu memory consumption as shown in /proc/meminfo
> also increases over time.
>
> In order to find out more information about those pages that pin
> offlined memcgs, the page_owner feature is extended to dump memory
> cgroup information especially whether the cgroup is offlined or not.
>
> Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> ---
> mm/page_owner.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index c52ce9d6bc3b..e5d8c642296b 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -10,6 +10,7 @@
> #include <linux/migrate.h>
> #include <linux/stackdepot.h>
> #include <linux/seq_file.h>
> +#include <linux/memcontrol.h>
> #include <linux/sched/clock.h>
>
> #include "internal.h"
> @@ -339,6 +340,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
> depot_stack_handle_t handle)
> {
> int ret = 0, pageblock_mt, page_mt;
> + unsigned long __maybe_unused memcg_data;
> char *kbuf;
>
> count = min_t(size_t, count, PAGE_SIZE);
> @@ -371,6 +373,32 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
> "Page has been migrated, last migrate reason: %s\n",
> migrate_reason_names[page_owner->last_migrate_reason]);
>
> +#ifdef CONFIG_MEMCG
> + /*
> + * Look for memcg information and print it out
> + */
> + memcg_data = READ_ONCE(page->memcg_data);
> + if (memcg_data) {
> + struct mem_cgroup *memcg = page_memcg_check(page);
> + bool onlined;
> + char name[80];
> +
> + if (memcg_data & MEMCG_DATA_OBJCGS)
> + SNPRINTF(kbuf, count, ret, err, "Slab cache page\n");
> +
> + if (!memcg)
> + goto copy_out;
> +
> + onlined = (memcg->css.flags & CSS_ONLINE);
> + cgroup_name(memcg->css.cgroup, name, sizeof(name) - 1);
> + SNPRINTF(kbuf, count, ret, err, "Charged %sto %smemcg %s\n",
^^^
Extra specifier?
Did this compile without warnings?
Ira
> + PageMemcgKmem(page) ? "(via objcg) " : "",
> + onlined ? "" : "offlined ", name);
> + }
> +
> +copy_out:
> +#endif
> +
> SNPRINTF(kbuf, count, ret, err, "\n");
>
> if (copy_to_user(buf, kbuf, ret))
> --
> 2.27.0
>
>
