From: Michal Hocko <mhocko@kernel.org>
To: Zefan Li <lizefan@huawei.com>
Cc: Roman Gushchin <guro@fb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Cgroups <cgroups@vger.kernel.org>,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Shakeel Butt <shakeelb@google.com>
Subject: Re: [PATCH v2] memcg: Fix memcg_kmem_bypass() for remote memcg charging
Date: Fri, 15 May 2020 10:34:58 +0200 [thread overview]
Message-ID: <20200515083458.GK29153@dhcp22.suse.cz> (raw)
In-Reply-To: <bad0e16b-7141-94c0-45f6-6ed03926b5f8@huawei.com>
On Fri 15-05-20 16:20:04, Li Zefan wrote:
> On 2020/5/15 14:56, Michal Hocko wrote:
> > On Thu 14-05-20 15:52:59, Roman Gushchin wrote:
[...]
> >>> I thought the user should ensure not do this, but now I think it makes sense to just bypass
> >>> the interrupt case.
> >>
> >> I think now it's mostly a legacy of the opt-out kernel memory accounting.
> >> Actually we can relax this requirement by forcibly overcommit the memory cgroup
> >> if the allocation is happening from the irq context, and punish it afterwards.
> >> Idk how much we wanna this, hopefully nobody is allocating large non-temporarily
> >> objects from an irq.
> >
> > I do not think we want to pretend that remote charging from the IRQ
> > context is supported. Why don't we simply WARN_ON(in_interrupt()) there?
> >
>
> How about:
>
> static inline bool memcg_kmem_bypass(void)
> {
> if (in_interrupt()) {
> WARN_ON(current->active_memcg);
> return true;
> }
Why not simply
if (WARN_ON_ONCE(in_interrupt())
return true;
the idea is that we want to catch any __GFP_ACCOUNT user from IRQ
context because this just doesn't work and we do not plan to support it
for now and foreseeable future. If this is reduced only to active_memcg
then we are only getting a partial picture.
>
> /* Allow remote memcg charging in kthread contexts. */
> if ((!current->mm || (current->flags & PF_KTHREAD)) && !current->active_memcg)
> return true;
> return false;
> }
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-05-15 8:35 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-13 7:28 [PATCH] memcg: Fix memcg_kmem_bypass() for remote memcg charging Zefan Li
2020-05-13 9:05 ` Michal Hocko
2020-05-13 11:19 ` Zefan Li
2020-05-13 11:29 ` Michal Hocko
2020-05-13 11:47 ` [PATCH v2] " Zefan Li
2020-05-13 12:22 ` Shakeel Butt
2020-05-13 13:05 ` Johannes Weiner
2020-05-13 16:11 ` Roman Gushchin
2020-05-14 1:16 ` Zefan Li
2020-05-14 22:52 ` Roman Gushchin
2020-05-15 6:56 ` Michal Hocko
2020-05-15 8:20 ` Zefan Li
2020-05-15 8:34 ` Michal Hocko [this message]
2020-05-15 16:22 ` Shakeel Butt
2020-05-15 17:31 ` Roman Gushchin
2020-05-18 9:13 ` Michal Hocko
2020-05-26 1:25 ` [PATCH v3] " Zefan Li
2020-05-26 15:53 ` Roman Gushchin
2020-05-27 16:50 ` Shakeel Butt
2020-05-28 14:44 ` Michal Hocko
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=20200515083458.GK29153@dhcp22.suse.cz \
--to=mhocko@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=cgroups@vger.kernel.org \
--cc=guro@fb.com \
--cc=hannes@cmpxchg.org \
--cc=linux-mm@kvack.org \
--cc=lizefan@huawei.com \
--cc=shakeelb@google.com \
--cc=vdavydov.dev@gmail.com \
/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).