From: Richard Palethorpe <rpalethorpe@suse.de>
To: "Michal Koutný" <mkoutny@suse.com>
Cc: Roman Gushchin <guro@fb.com>,
ltp@lists.linux.it, Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>,
Shakeel Butt <shakeelb@google.com>,
Christoph Lameter <cl@linux.com>,
Michal Hocko <mhocko@kernel.org>, Tejun Heo <tj@kernel.org>,
Vlastimil Babka <vbabka@suse.cz>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] mm: memcg/slab: Stop reparented obj_cgroups from charging root
Date: Fri, 16 Oct 2020 11:41:43 +0100 [thread overview]
Message-ID: <87sgaesba0.fsf@suse.de> (raw)
In-Reply-To: <20201016094702.GA95052@blackbook>
Hello Michal,
Michal Koutný <mkoutny@suse.com> writes:
> Hello.
>
> On Wed, Oct 14, 2020 at 08:07:49PM +0100, Richard Palethorpe <rpalethorpe@suse.com> wrote:
>> SLAB objects which outlive their memcg are moved to their parent
>> memcg where they may be uncharged. However if they are moved to the
>> root memcg, uncharging will result in negative page counter values as
>> root has no page counters.
> Why do you think those are reparented objects? If those are originally
> charged in a non-root cgroup, then the charge value should be propagated up the
> hierarchy, including root memcg, so if they're later uncharged in root
> after reparenting, it should still break even. (Or did I miss some stock
> imbalance?)
I traced it and can see they are reparented objects and that the root
groups counters are zero (or negative if I run madvise06 multiple times)
before a drain takes place. I'm guessing this is because the root group
has 'use_hierachy' set to false so that the childs page_counter parents
are set to NULL. However I will check, because I'm not sure about
either.
>
> (But the patch seems justifiable to me as objects (not)charged directly to
> root memcg may be incorrectly uncharged.)
>
> Thanks,
> Michal
--
Thank you,
Richard.
next prev parent reply other threads:[~2020-10-16 10:41 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-14 19:07 [RFC PATCH] mm: memcg/slab: Stop reparented obj_cgroups from charging root Richard Palethorpe
2020-10-14 20:08 ` Roman Gushchin
2020-10-16 5:40 ` Richard Palethorpe
2020-10-16 9:47 ` Michal Koutný
2020-10-16 10:41 ` Richard Palethorpe [this message]
2020-10-16 15:05 ` Richard Palethorpe
2020-10-16 17:26 ` Michal Koutný
2020-10-16 14:53 ` Johannes Weiner
2020-10-16 17:02 ` Roman Gushchin
2020-10-16 17:15 ` Michal Koutný
2020-10-19 8:45 ` Richard Palethorpe
2020-10-19 9:58 ` [PATCH v3] " Richard Palethorpe
2020-10-19 16:58 ` Shakeel Butt
2020-10-20 5:52 ` Richard Palethorpe
2020-10-20 13:49 ` Richard Palethorpe
2020-10-20 16:56 ` Shakeel Butt
2020-10-21 20:32 ` Roman Gushchin
2020-10-20 17:24 ` Michal Koutný
2020-10-22 7:04 ` Richard Palethorpe
2020-10-22 12:28 ` [PATCH v4] " Richard Palethorpe
2020-10-22 16:37 ` Shakeel Butt
2020-10-22 17:25 ` Roman Gushchin
2020-10-22 23:59 ` Shakeel Butt
2020-10-23 0:40 ` Roman Gushchin
2020-10-23 15:44 ` Johannes Weiner
2020-10-23 16:41 ` Shakeel Butt
2020-10-26 7:32 ` Richard Palethorpe
2020-10-26 23:14 ` Roman Gushchin
2020-10-19 22:28 ` [RFC PATCH] " Roman Gushchin
2020-10-20 6:04 ` Richard Palethorpe
2020-10-20 12:02 ` Richard Palethorpe
2020-10-20 14:48 ` Richard Palethorpe
2020-10-20 16:27 ` Michal Koutný
2020-10-20 17:07 ` Roman Gushchin
2020-10-20 18:18 ` Johannes Weiner
2020-10-21 19:33 ` Roman Gushchin
2020-10-23 16:30 ` Johannes Weiner
2020-11-10 1:27 ` Roman Gushchin
2020-11-10 15:11 ` Shakeel Butt
2020-11-10 19:13 ` Roman Gushchin
2020-11-20 17:46 ` Michal Koutný
2020-11-03 13:22 ` Michal Hocko
2020-11-03 21:30 ` Roman Gushchin
2020-10-20 16:55 ` Shakeel Butt
2020-10-20 17:17 ` Roman Gushchin
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