Re: hugetlb pages not accounted for in rss

Mike Kravetz
2015-07-28T21:15:46Z

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
>