Re: [PATCH] fs, mm: account filp and names caches to kmemcg

From: Johannes Weiner <hannes@cmpxchg.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Greg Thelen <gthelen@google.com>,
	Shakeel Butt <shakeelb@google.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux MM <linux-mm@kvack.org>,
	linux-fsdevel@vger.kernel.org,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] fs, mm: account filp and names caches to kmemcg
Date: Tue, 24 Oct 2017 11:45:11 -0400	[thread overview]
Message-ID: <20171024154511.GA32340@cmpxchg.org> (raw)
In-Reply-To: <20171013063555.pa7uco43mod7vrkn@dhcp22.suse.cz>

On Fri, Oct 13, 2017 at 08:35:55AM +0200, Michal Hocko wrote:
> On Thu 12-10-17 15:03:12, Johannes Weiner wrote:
> > All I'm saying is that, when the syscall-context fails to charge, we
> > should do mem_cgroup_oom() to set up the async OOM killer, let the
> > charge succeed over the hard limit - since the OOM killer will most
> > likely get us back below the limit - then mem_cgroup_oom_synchronize()
> > before the syscall returns to userspace.
> 
> OK, then we are on the same page now. Your initial wording didn't
> mention async OOM killer. This makes more sense. Although I would argue
> that we can retry the charge as long as out_of_memory finds a victim.
> This would return ENOMEM to the pathological cases where no victims
> could be found.

I think that's much worse because it's even harder to test and verify
your applications against.

If syscalls can return -ENOMEM on OOM, they should do so reliably.