Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: Shakeel Butt <shakeelb@google.com>
To: rpalethorpe@suse.de
Cc: Linux MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	 LTP List <ltp@lists.linux.it>, Roman Gushchin <guro@fb.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	 Andrew Morton <akpm@linux-foundation.org>,
	Christoph Lameter <cl@linux.com>,
	 Michal Hocko <mhocko@kernel.org>, Tejun Heo <tj@kernel.org>,
	Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v3] mm: memcg/slab: Stop reparented obj_cgroups from charging root
Date: Tue, 20 Oct 2020 09:56:51 -0700
Message-ID: <CALvZod45mAzyo9LNR4YtX_3J0gZJDagYTNv8NbJAuXzwK5A2DA@mail.gmail.com> (raw)
In-Reply-To: <87eeltvwg4.fsf@suse.de>

On Tue, Oct 20, 2020 at 6:49 AM Richard Palethorpe <rpalethorpe@suse.de> wrote:
>
> Hello,
>
> Richard Palethorpe <rpalethorpe@suse.de> writes:
>
> > Hello Shakeel,
> >
> > Shakeel Butt <shakeelb@google.com> writes:
> >>>
> >>> V3: Handle common case where use_hierarchy=1 and update description.
> >>>
> >>>  mm/memcontrol.c | 7 +++++--
> >>>  1 file changed, 5 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >>> index 6877c765b8d0..34b8c4a66853 100644
> >>> --- a/mm/memcontrol.c
> >>> +++ b/mm/memcontrol.c
> >>> @@ -291,7 +291,7 @@ static void obj_cgroup_release(struct percpu_ref *ref)
> >>>
> >>>         spin_lock_irqsave(&css_set_lock, flags);
> >>>         memcg = obj_cgroup_memcg(objcg);
> >>> -       if (nr_pages)
> >>> +       if (nr_pages && (!mem_cgroup_is_root(memcg) || memcg->use_hierarchy))
> >>
> >> If we have non-root memcg with use_hierarchy as 0 and this objcg was
> >> reparented then this __memcg_kmem_uncharge() can potentially underflow
> >> the page counter and give the same warning.
> >
> > Yes, although the kernel considers such a config to be broken, and
> > prints a warning to the log, it does allow it.
>
> Actually this can not happen because if use_hierarchy=0 then the objcg
> will be reparented to root.
>

Yup, you are right. I do wonder if we should completely deprecate
use_hierarchy=0.


  reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-14 19:07 [RFC PATCH] " 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
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 [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CALvZod45mAzyo9LNR4YtX_3J0gZJDagYTNv8NbJAuXzwK5A2DA@mail.gmail.com \
    --to=shakeelb@google.com \
    --cc=akpm@linux-foundation.org \
    --cc=cl@linux.com \
    --cc=guro@fb.com \
    --cc=hannes@cmpxchg.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=ltp@lists.linux.it \
    --cc=mhocko@kernel.org \
    --cc=rpalethorpe@suse.de \
    --cc=tj@kernel.org \
    --cc=vbabka@suse.cz \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git