linux-kernel - Re: [PATCH v2 3/3] mm/page_owner: Dump memcg information

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Message-ID: <82c99093-e44b-7fac-14ab-9e8392d107ea@redhat.com>
Date:   Sun, 30 Jan 2022 13:22:46 -0500
From:   Waiman Long <longman@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Johannes Weiner <hannes@...xchg.org>,
        Michal Hocko <mhocko@...nel.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        linux-mm@...ck.org, Ira Weiny <ira.weiny@...el.com>,
        Rafael Aquini <aquini@...hat.com>
Subject: Re: [PATCH v2 3/3] mm/page_owner: Dump memcg information

On 1/30/22 01:33, Mike Rapoport wrote:
> On Sat, Jan 29, 2022 at 03:53:15PM -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 | 31 +++++++++++++++++++++++++++++++
>>   1 file changed, 31 insertions(+)
>>
>> diff --git a/mm/page_owner.c b/mm/page_owner.c
>> index 28dac73e0542..8dc5cd0fa227 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"
>> @@ -331,6 +332,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
>>   		depot_stack_handle_t handle)
>>   {
>>   	int ret, pageblock_mt, page_mt;
>> +	unsigned long __maybe_unused memcg_data;
>>   	char *kbuf;
>>   
>>   	count = min_t(size_t, count, PAGE_SIZE);
>> @@ -365,6 +367,35 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
>>   			migrate_reason_names[page_owner->last_migrate_reason]);
>>   	}
>>   
>> +#ifdef CONFIG_MEMCG
> Can we put all this along with the declaration of memcg_data in a helper
> function please?
>
Sure. Will post another version with that change.

Cheers,
Longman