On 10/13/2016 05:19 AM, Jan Stancek wrote:
> Hi,
>
> I'm running into ENOMEM failures with libhugetlbfs testsuite [1] on
> a power8 lpar system running 4.8 or latest git [2]. Repeated runs of
> this suite trigger multiple OOMs, that eventually kill entire system,
> it usually takes 3-5 runs:
>
> * Total System Memory......: 18024 MB
> * Shared Mem Max Mapping...: 320 MB
> * System Huge Page Size....: 16 MB
> * Available Huge Pages.....: 20
> * Total size of Huge Pages.: 320 MB
> * Remaining System Memory..: 17704 MB
> * Huge Page User Group.....: hugepages (1001)
>
> I see this only on ppc (BE/LE), x86_64 seems unaffected and successfully
> ran the tests for ~12 hours.
>
> Bisect has identified following patch as culprit:
> commit 67961f9db8c477026ea20ce05761bde6f8bf85b0
> Author: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> Date: Wed Jun 8 15:33:42 2016 -0700
> mm/hugetlb: fix huge page reserve accounting for private mappings
>
Thanks Jan, I'll take a look.
>
> Following patch (made with my limited insight) applied to
> latest git [2] fixes the problem for me:
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index ec49d9e..7261583 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1876,7 +1876,7 @@ static long __vma_reservation_common(struct hstate *h,
> * return value of this routine is the opposite of the
> * value returned from reserve map manipulation routines above.
> */
> - if (ret)
> + if (ret >= 0)
> return 0;
> else
> return 1;
>
Do note that this code is only executed if this condition is true:
else if (is_vma_resv_set(vma, HPAGE_RESV_OWNER) && ret >= 0) {
So, we would always return 0. This always tells the calling code that a
reservation exists.
--
Mike Kravetz
> Regards,
> Jan
>
> [1] https://github.com/libhugetlbfs/libhugetlbfs
> [2] v4.8-14230-gb67be92
>
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