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SubjectRe: [RFC PATCH 2/4] hugetlb: add support for preferred node to alloc_huge_page_nodemask
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On 06/14/2017 03:12 PM, Mike Kravetz wrote:
> On 06/13/2017 02:00 AM, Michal Hocko wrote:
>> From: Michal Hocko <mhocko@suse.com>
>>
>> alloc_huge_page_nodemask tries to allocate from any numa node in the
>> allowed node mask starting from lower numa nodes. This might lead to
>> filling up those low NUMA nodes while others are not used. We can reduce
>> this risk by introducing a concept of the preferred node similar to what
>> we have in the regular page allocator. We will start allocating from the
>> preferred nid and then iterate over all allowed nodes in the zonelist
>> order until we try them all.
>>
>> This is mimicking the page allocator logic except it operates on
>> per-node mempools. dequeue_huge_page_vma already does this so distill
>> the zonelist logic into a more generic dequeue_huge_page_nodemask
>> and use it in alloc_huge_page_nodemask.
>>
>> Signed-off-by: Michal Hocko <mhocko@suse.com>
>> ---
>
>
> I built attempts/hugetlb-zonelists, threw it on a test machine, ran the
> libhugetlbfs test suite and saw failures. The failures started with this
> patch: commit 7e8b09f14495 in your tree. I have not yet started to look
> into the failures. It is even possible that the tests are making bad
> assumptions, but there certainly appears to be changes in behavior visible
> to the application(s).

nm. The failures were the result of dequeue_huge_page_nodemask() always
returning NULL. Vlastimil already noticed this issue and provided a
solution.

--
Mike Kravetz

>
> FYI - My 'test machine' is an x86 KVM insatnce with 8GB memory simulating
> 2 nodes. Huge page allocations before running tests:
> node0
> 512 free_hugepages
> 512 nr_hugepages
> 0 surplus_hugepages
> node1
> 512 free_hugepages
> 512 nr_hugepages
> 0 surplus_hugepages
>
> I can take a closer look at the failures tomorrow.
>

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