linux-kernel - Re: Memory leaks on atom-based boards?

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Date:	Mon, 10 Nov 2014 00:19:56 -0000
From:	"AL13N" <alien@...il.be>
To:	linux-kernel@...r.kernel.org
Cc:	"Vlastimil Babka" <vbabka@...e.cz>
Subject: Re: Memory leaks on atom-based boards?

> On 11/09/2014 05:38 PM, AL13N wrote:
>>> On 10/27/2014 07:44 PM, AL13N wrote:
>>>
>>> Hi, this does look like a kernel memory leak. There was recently a
>>> known
>>> one fixed by patch from https://lkml.org/lkml/2014/10/15/447 which made
>>> it to 3.18-rc3 and should be backported to stable kernels 3.8+ soon.
>>> You would recognize if this is the fix for you by checking the
>>> thp_zero_page_alloc value in /proc/vmstat. Value X > 1 basically means
>>> that X*2 MB memory is leaked.
>>> You say in the serverfault post that 3.17.2 helped, but the fix is not
>>> in 3.17.2... but it could be just that the circumstances changed and
>>> THP
>>> zero pages are no longer freed and realocated.
>>> So if you want to be sure, I would suggest trying again a version where
>>> the problem appeared on your system, and checking the
>>> thp_zero_page_alloc. Perhaps you'll see a >1 value even on 3.17.2,
>>> which
>>> means some leak did occur there as well, but maybe not so severe.
>>
>>
>> i was gonna tell you guys, but i was waiting until i was sure, but
>> indeed
>> 3.17.2 fixed, it, where i had OOM after 3, maybe 4 days (for at least 2
>> months), now i'm up more than 4 days and the MemAvailable is still high
>> enough... at about 3.5GB whereas otherwise it would dwindle until 0. (at
>> about 1GB/day)
>>
>> Well, it results to 0 on 3.17.2 ... so... i guess not? i'll keep this
>> value under observation...
>
> Hm, 0 sounds like nobody was allocating transparent huge pages at all.
> What
> about the other thp_* stats?

thp_fault_alloc 0
thp_fault_fallback 0
thp_collapse_alloc 0
thp_collapse_alloc_failed 0
thp_split 0
thp_zero_page_alloc 0
thp_zero_page_alloc_failed 0


i guess on 3.17.2 there's something that doesn't allocate thp? either
that, or it was a different issue after all...

>>>>  - How can i find out what is allocating all this memory?
>>>
>>> There's no simple way, unfortunately. Checking the kpageflags /proc
>>> file
>>> might help. IIRC there used to be a patch in -mm tree to store who
>>> allocated what page, but it might be bitrotten.
>>
>>
>> i checked what was in kpageflags (or kpagecount) but it's all some kind
>> of
>> binary stuff...
>>
>> do i need some tool to interprete these values?
>
> There's tools/vm/page-types.c in kernel sources which can read kpageflags,
> but
> not the kpagecount...

good to know...

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