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Date: Fri, 28 Jan 2022 22:35:22 -0500 From: Waiman Long <longman@...hat.com> To: Ira Weiny <ira.weiny@...el.com> Cc: Johannes Weiner <hannes@...xchg.org>, Michal Hocko <mhocko@...nel.org>, Vladimir Davydov <vdavydov.dev@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org, linux-mm@...ck.org, Rafael Aquini <aquini@...hat.com> Subject: Re: [PATCH 2/2] mm/page_owner: Dump memcg information On 1/28/22 16:48, Ira Weiny wrote: > On Fri, Jan 28, 2022 at 04:31:07PM -0500, Waiman Long wrote: >> On 1/28/22 16:22, Ira Weiny wrote: >>> 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@...hat.com> >>>> --- >>>> 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? >> Yes, there was no warning. > But isn't that an extra specifier? There are 3 arguments to the format string that match the 3 "%s" in it: 1) PageMemcgKmem(page) ? "(via objcg) " : "" 2) onlined ? "" : "offlined 3) name Cheers, Longman
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