Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
From: "Michal Koutný" <mkoutny@suse.com>
To: Roman Gushchin <guro@fb.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Dennis Zhou <dennis@kernel.org>, Tejun Heo <tj@kernel.org>,
	Christoph Lameter <cl@linux.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Shakeel Butt <shakeelb@google.com>,
	linux-mm@kvack.org, kernel-team@fb.com,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 4/5] mm: memcg: charge memcg percpu memory to the parent cgroup
Date: Tue, 11 Aug 2020 16:47:54 +0200
Message-ID: <20200811144754.GA45201@blackbook> (raw)
In-Reply-To: <20200807043717.GA1231562@carbon.DHCP.thefacebook.com>


[-- Attachment #1: Type: text/plain, Size: 2436 bytes --]

On Thu, Aug 06, 2020 at 09:37:17PM -0700, Roman Gushchin <guro@fb.com> wrote:
> In general, yes. But in this case I think it wouldn't be a good idea:
> most often cgroups are created by a centralized daemon (systemd),
> which is usually located in the root cgroup. Even if it's located not in
> the root cgroup, limiting it's memory will likely affect the whole system,
> even if only one specific limit was reached.
The generic scheme would be (assuming the no internal process
constraint, in the root too)

` root or delegated root
  ` manager-cgroup (systemd, docker, ...)
  ` [aggregation group(s)]
    ` job-group-1
    ` ...
    ` job-group-n

> If there is a containerized workload, which creates sub-cgroups,
> charging it's parent cgroup is perfectly effective.
No dispute about this in either approaches.

> And the opposite, if we'll charge the cgroup of a process, who created
> a cgroup, we'll not cover the most common case: systemd creating
> cgroups for all services in the system.
What I mean is that systemd should be charged for the cgroup creation.
Or more generally, any container/cgroup manager should be charged.
Consider a leak when it wouldn't remove spent cgroups, IMO the effect
(throttling, reclaim) should be exercised on such a culprit.

I don't think the existing workload (job-group-i above) should
unnecessarily suffer when only manager is acting up. Is that different
from your idea?

> Right, but it's quite unusual for tasks from one cgroup to create sub-cgroups
> in completely different cgroup. In this particular case there are tons of other
> ways how a task from C00 can hurt C1.
I agree with that.


If I haven't overlooked anything, this should be first case when
cgroup-related structures are accounted (please correct me).
So this is setting a precendent, if others show useful to be accounted
in the future too. I'm thinking about cpu_cgroup_css_alloc() that can
also allocate a lot (with big CPU count). The current approach would lead
situations where matching cpu and memory csses needn't to exist and that
would need special handling.


> On Thu, Aug 06, 2020 at 09:16:03PM -0700, Andrew Morton wrote:
> > These week-old issues appear to be significant.  Roman?  Or someone
> > else?
Despite my concerns, I don't think this is fundamental and can't be
changed later so it doesn't prevent the inclusion in 5.9 RC1.

Regards,
Michal

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

  parent reply index

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23 18:45 [PATCH v3 0/5] mm: memcg accounting of percpu memory Roman Gushchin
2020-06-23 18:45 ` [PATCH v3 1/5] percpu: return number of released bytes from pcpu_free_area() Roman Gushchin
2020-06-24  0:58   ` Shakeel Butt
2020-06-23 18:45 ` [PATCH v3 2/5] mm: memcg/percpu: account percpu memory to memory cgroups Roman Gushchin
2020-06-24  1:25   ` Shakeel Butt
2020-06-23 18:45 ` [PATCH v3 3/5] mm: memcg/percpu: per-memcg percpu memory statistics Roman Gushchin
2020-06-24  1:35   ` Shakeel Butt
2020-08-11 15:05   ` Johannes Weiner
2020-06-23 18:45 ` [PATCH v3 4/5] mm: memcg: charge memcg percpu memory to the parent cgroup Roman Gushchin
2020-06-24  1:40   ` Shakeel Butt
2020-06-24  1:49     ` Roman Gushchin
2020-07-29 17:10   ` Michal Koutný
2020-08-07  4:16     ` Andrew Morton
2020-08-07  4:37       ` Roman Gushchin
2020-08-10 19:33         ` Roman Gushchin
2020-08-11 14:47         ` Michal Koutný [this message]
2020-08-11 16:55           ` Roman Gushchin
2020-08-11 18:32             ` Michal Koutný
2020-08-11 19:32               ` Roman Gushchin
2020-08-12 16:28                 ` Michal Koutný
2020-08-11 15:27   ` Johannes Weiner
2020-08-11 17:06     ` Roman Gushchin
2020-08-13  9:16       ` Naresh Kamboju
2020-08-13 23:27         ` Stephen Rothwell

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=20200811144754.GA45201@blackbook \
    --to=mkoutny@suse.com \
    --cc=akpm@linux-foundation.org \
    --cc=cl@linux.com \
    --cc=dennis@kernel.org \
    --cc=guro@fb.com \
    --cc=hannes@cmpxchg.org \
    --cc=kernel-team@fb.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@kernel.org \
    --cc=shakeelb@google.com \
    --cc=tj@kernel.org \
    /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