linux-kernel - Re: hugetlb pages not accounted for in rss

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Message-ID: <55B7F0F8.8080909@oracle.com>
Date:	Tue, 28 Jul 2015 14:15:36 -0700
From:	Mike Kravetz <mike.kravetz@...cle.com>
To:	Jörn Engel <joern@...estorage.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: hugetlb pages not accounted for in rss

On 07/28/2015 11:32 AM, Jörn Engel wrote:
> On Mon, Jul 27, 2015 at 04:26:47PM -0700, Mike Kravetz wrote:
>> I started looking at the hugetlb self tests.  The test hugetlbfstest
>> expects hugetlb pages to be accounted for in rss.  However, there is
>> no code in the kernel to do this accounting.
>>
>> It looks like there was an effort to add the accounting back in 2013.
>> The test program made it into tree, but the accounting code did not.
>
> My apologies.  Upstream work always gets axed first when I run out of
> time - which happens more often than not.

No worries, I just noticed the inconsistency of the test program and
no supporting code in the kernel.

>> The easiest way to resolve this issue would be to remove the test and
>> perhaps document that hugetlb pages are not accounted for in rss.
>> However, it does seem like a big oversight that hugetlb pages are not
>> accounted for in rss.  From a quick scan of the code it appears THP
>> pages are properly accounted for.
>>
>> Thoughts?
>
> Unsurprisingly I agree that hugepages should count towards rss.  Keeping
> the test in keeps us honest.  Actually fixing the issue would make us
> honest and correct.
>
> Increasingly we have tiny processes (by rss) that actually consume large
> fractions of total memory.  Makes rss somewhat useless as a measure of
> anything.

I'll take a look at what it would take to get the accounting in place.
-- 
Mike Kravetz

>
> Jörn
>
> --
> Consensus is no proof!
> -- John Naisbitt
>
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