From: Michal Hocko <mhocko@kernel.org>
To: Minchan Kim <minchan@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@techsingularity.net>,
Vlastimil Babka <vbabka@suse.cz>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Sangseok Lee <sangseok.lee@lge.com>
Subject: Re: [PATCH 0/4] use up highorder free pages before OOM
Date: Mon, 10 Oct 2016 09:47:31 +0200 [thread overview]
Message-ID: <20161010074724.GC20420@dhcp22.suse.cz> (raw)
In-Reply-To: <20161007150425.GD3060@bbox>
On Sat 08-10-16 00:04:25, Minchan Kim wrote:
[...]
> I can show other log which reserve greater than 1%. See the DMA32 zone
> free pages. It was GFP_ATOMIC allocation so it's different with I posted
> but important thing is VM can reserve memory greater than 1% by the race
> which was really what we want.
>
> in:imklog: page allocation failure: order:0, mode:0x2280020(GFP_ATOMIC|__GFP_NOTRACK)
[...]
> DMA: 7*4kB (UE) 3*8kB (UH) 1*16kB (M) 0*32kB 2*64kB (U) 1*128kB (M) 1*256kB (U) 0*512kB 1*1024kB (U) 1*2048kB (U) 1*4096kB (H) = 7748kB
> DMA32: 10*4kB (H) 3*8kB (H) 47*16kB (H) 38*32kB (H) 5*64kB (H) 1*128kB (H) 2*256kB (H) 3*512kB (H) 3*1024kB (H) 3*2048kB (H) 4*4096kB (H) = 30128kB
Yes, this sounds like a bug. Please add this information to the patch
which aims to fix the misaccounting.
> > So while I do agree that potential issues - misaccounting and others you
> > are addressing in the follow up patch - are good to fix but I believe that
> > draining last 19M is not something that would reliably get you over the
> > edge. Your workload (93% of memory sitting on anon LRU with swap full)
> > simply doesn't fit into the amount of memory you have available.
>
> What happens if the workload fit into additional 19M memory?
> I admit my testing aimed for proving the problem but with this patchset,
> there is no OOM killing with many free pages and the number of OOM was
> reduced highly. It is definitely better than old.
>
> Please don't ignore 1% memory in embedded system. 20M memory in 2G system,
> If we can use those for zram, it is 60~80M memory via compression.
> You should know how many engineers try to reduce 1M of their driver to
> cost down of the product, seriously.
I am definitely not ignoring neither embedded systems nor 1% of the
memory that might really matter. I just wanted to point out that being
that close to OOM usually blows up later or starts trashing very soon.
It is true that a particular workload might benefit from ever last
allocatable page in the system but it would be better to mention all
that in the changelog.
--
Michal Hocko
SUSE Labs
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next prev parent reply other threads:[~2016-10-10 7:47 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-07 5:45 [PATCH 0/4] use up highorder free pages before OOM Minchan Kim
2016-10-07 5:45 ` [PATCH 1/4] mm: adjust reserved highatomic count Minchan Kim
2016-10-07 12:30 ` Vlastimil Babka
2016-10-07 14:29 ` Minchan Kim
2016-10-10 6:57 ` Vlastimil Babka
2016-10-11 4:19 ` Minchan Kim
2016-10-11 9:40 ` Vlastimil Babka
2016-10-12 5:36 ` Mel Gorman
2016-10-07 5:45 ` [PATCH 2/4] mm: prevent double decrease of nr_reserved_highatomic Minchan Kim
2016-10-07 12:44 ` Vlastimil Babka
2016-10-07 14:30 ` Minchan Kim
2016-10-12 5:36 ` Mel Gorman
2016-10-07 5:45 ` [PATCH 3/4] mm: unreserve highatomic free pages fully before OOM Minchan Kim
2016-10-07 9:09 ` Michal Hocko
2016-10-07 14:43 ` Minchan Kim
2016-10-10 7:41 ` Michal Hocko
2016-10-11 5:01 ` Minchan Kim
2016-10-11 6:50 ` Michal Hocko
2016-10-11 7:09 ` Minchan Kim
2016-10-11 7:26 ` Michal Hocko
2016-10-11 7:37 ` Minchan Kim
2016-10-11 8:01 ` Michal Hocko
2016-10-07 5:45 ` [PATCH 4/4] mm: skip to reserve pageblock crossed zone boundary for HIGHATOMIC Minchan Kim
2016-10-07 9:16 ` [PATCH 0/4] use up highorder free pages before OOM Michal Hocko
2016-10-07 15:04 ` Minchan Kim
2016-10-10 7:47 ` Michal Hocko [this message]
2016-10-11 5:06 ` Minchan Kim
2016-10-11 6:53 ` Michal Hocko
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