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From: Johannes Weiner <hannes@cmpxchg.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Roman Gushchin <guro@fb.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH] mm: fix false-positive OVERCOMMIT_GUESS failures
Date: Wed, 17 Apr 2019 11:05:51 -0400	[thread overview]
Message-ID: <20190417150551.GA23013@cmpxchg.org> (raw)
In-Reply-To: <0d2ad7c1-4a5f-08b0-0f57-0273fedc4f70@suse.cz>

On Wed, Apr 17, 2019 at 02:04:17PM +0200, Vlastimil Babka wrote:
> On 4/12/19 10:06 PM, Roman Gushchin wrote:
> > On Fri, Apr 12, 2019 at 03:14:18PM -0400, Johannes Weiner wrote:
> >> With the default overcommit==guess we occasionally run into mmap
> >> rejections despite plenty of memory that would get dropped under
> >> pressure but just isn't accounted reclaimable. One example of this is
> >> dying cgroups pinned by some page cache. A previous case was auxiliary
> >> path name memory associated with dentries; we have since annotated
> >> those allocations to avoid overcommit failures (see d79f7aa496fc ("mm:
> >> treat indirectly reclaimable memory as free in overcommit logic")).
> >>
> >> But trying to classify all allocated memory reliably as reclaimable
> >> and unreclaimable is a bit of a fool's errand. There could be a myriad
> >> of dependencies that constantly change with kernel versions.
> 
> Just wondering, did you find at least one another reclaimable case like
> those path names?

I'm only aware of the cgroup structures which can be pinned by a
dentry, inode, or page cache page. But they're an entire tree of
memory allocations, per-cpu memory regions etc. that would be
impossible to annotate correctly; it's also unreclaimable while the
cgroup is user-visible and only becomes reclaimable once rmdir'd.


      reply	other threads:[~2019-04-17 15:05 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-12 19:14 [PATCH] mm: fix false-positive OVERCOMMIT_GUESS failures Johannes Weiner
2019-04-12 20:06 ` Roman Gushchin
2019-04-17 12:04   ` Vlastimil Babka
2019-04-17 15:05     ` Johannes Weiner [this message]

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