linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Chris Down <chris@chrisdown.name>
To: legion@kernel.org
Cc: LKML <linux-kernel@vger.kernel.org>,
	Linux Containers <containers@lists.linux.dev>,
	Linux Containers <containers@lists.linux-foundation.org>,
	Linux FS Devel <linux-fsdevel@vger.kernel.org>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	"Eric W . Biederman" <ebiederm@xmission.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH v1] proc: Implement /proc/self/meminfo
Date: Thu, 3 Jun 2021 12:33:58 +0100	[thread overview]
Message-ID: <YLi+JoBwfLtqVGiP@chrisdown.name> (raw)
In-Reply-To: <ac070cd90c0d45b7a554366f235262fa5c566435.1622716926.git.legion@kernel.org>

Hi Alexey,

legion@kernel.org writes:
>From: Alexey Gladkov <legion@kernel.org>
>The /proc/meminfo contains information regardless of the cgroups
>restrictions. This file is still widely used [1]. This means that all
>these programs will not work correctly inside container [2][3][4]. Some
>programs try to respect the cgroups limits, but not all of them
>implement support for all cgroup versions [5].
>
>Correct information can be obtained from cgroups, but this requires the
>cgroups to be available inside container and the correct version of
>cgroups to be supported.

Then they should add support for it. We already export these metrics as part of 
cgroups and plenty of applications like Docker, podman, containerd, systemd, 
runc, etc already support it.

Putting stuff in /proc to get around the problem of "some other metric I need 
might not be exported to a container" is not a very compelling argument. If 
they want it, then export it to the container...

Ultimately, if they're going to have to add support for a new 
/proc/self/meminfo file anyway, these use cases should just do it properly 
through the already supported APIs.

>+	for_each_online_node(nid)
>+		mem_cgroup_nr_pages(memcg, nid, mi->pages);
>+
>+	mi->slab_reclaimable = memcg_page_state(memcg, NR_SLAB_RECLAIMABLE_B);
>+	mi->slab_unreclaimable = memcg_page_state(memcg, NR_SLAB_UNRECLAIMABLE_B);
>+	mi->cached = memcg_page_state(memcg, NR_FILE_PAGES);
>+	mi->swapcached = memcg_page_state(memcg, NR_SWAPCACHE);
>+	mi->anon_pages = memcg_page_state(memcg, NR_ANON_MAPPED);
>+	mi->mapped = memcg_page_state(memcg, NR_FILE_MAPPED);
>+	mi->nr_pagetable = memcg_page_state(memcg, NR_PAGETABLE);
>+	mi->dirty_pages = memcg_page_state(memcg, NR_FILE_DIRTY);
>+	mi->writeback_pages = memcg_page_state(memcg, NR_WRITEBACK);
>+}

This presents an extraordinarily confusing API. A cgroup can contain more than 
one process, so it's not right to present this information as "meminfo" in 
/proc/self when these statistics may not have any relation to the current task 
under question.

  parent reply	other threads:[~2021-06-03 11:35 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-03 10:43 [PATCH v1] proc: Implement /proc/self/meminfo legion
2021-06-03 11:33 ` Michal Hocko
2021-06-03 11:33 ` Chris Down [this message]
2021-06-09  8:16   ` Enrico Weigelt, metux IT consult
2021-06-09 19:14     ` Eric W. Biederman
2021-06-09 20:31       ` Johannes Weiner
2021-06-09 20:56         ` Eric W. Biederman
2021-06-10  0:36           ` Daniel Walsh
2021-06-11 10:37         ` Enrico Weigelt, metux IT consult
2021-06-15 11:32 ` Christian Brauner
2021-06-15 12:47   ` Alexey Gladkov
2021-06-16  1:09     ` Shakeel Butt
2021-06-16 16:17       ` Eric W. Biederman
2021-06-18 17:03         ` Michal Hocko
2021-06-18 23:38         ` Shakeel Butt
2021-06-21 18:20           ` Enrico Weigelt, metux IT consult

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=YLi+JoBwfLtqVGiP@chrisdown.name \
    --to=chris@chrisdown.name \
    --cc=akpm@linux-foundation.org \
    --cc=christian.brauner@ubuntu.com \
    --cc=containers@lists.linux-foundation.org \
    --cc=containers@lists.linux.dev \
    --cc=ebiederm@xmission.com \
    --cc=hannes@cmpxchg.org \
    --cc=legion@kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mhocko@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
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).