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From: "Michal Koutný" <mkoutny@suse.com>
To: Richard Palethorpe <rpalethorpe@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 11:47:02 +0200	[thread overview]
Message-ID: <20201016094702.GA95052@blackbook> (raw)
In-Reply-To: <20201014190749.24607-1-rpalethorpe@suse.com>

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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?)

(But the patch seems justifiable to me as objects (not)charged directly to
root memcg may be incorrectly uncharged.)

Thanks,
Michal

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  parent reply	other threads:[~2020-10-16  9:47 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 [this message]
2020-10-16 10:41   ` Richard Palethorpe
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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