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

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Date:   Sun, 30 Jan 2022 12:51:00 -0800 (PST)
From:   David Rientjes <rientjes@...gle.com>
To:     Waiman Long <longman@...hat.com>
cc:     Mike Rapoport <rppt@...nel.org>,
        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 Sun, 30 Jan 2022, Waiman Long wrote:

> 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.
> 

That would certainly make it much cleaner.  After that's done (and perhaps 
addressing my nit comment in the first patch), feel free to add

	Acked-by: David Rientjes <rientjes@...gle.com>

to all three patches.

Thanks!