On Tue, 20 Oct 2015 12:53:17 -0700 Dave Hansen <dave@xxxxxxxx> wrote:
>
> From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
>
> I have a hugetlbfs user which is never explicitly allocating huge pages
> with 'nr_hugepages'. They only set 'nr_overcommit_hugepages' and then let
> the pages be allocated from the buddy allocator at fault time.
>
> This works, but they noticed that mbind() was not doing them any good and
> the pages were being allocated without respect for the policy they
> specified.
>
> The code in question is this:
>
> > struct page *alloc_huge_page(struct vm_area_struct *vma,
> ...
> > page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve, gbl_chg);
> > if (!page) {
> > page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
>
> dequeue_huge_page_vma() is smart and will respect the VMA's memory policy.
> But, it only grabs _existing_ huge pages from the huge page pool. If the
> pool is empty, we fall back to alloc_buddy_huge_page() which obviously
> can't do anything with the VMA's policy because it isn't even passed the
> VMA.
>
> Almost everybody preallocates huge pages. That's probably why nobody has
> ever noticed this. Looking back at the git history, I don't think this
> _ever_ worked from when alloc_buddy_huge_page() was introduced in 7893d1d5,
> 8 years ago.
>
> The fix is to pass vma/addr down in to the places where we actually call in
> to the buddy allocator. It's fairly straightforward plumbing. This has
> been lightly tested.
huh. Fair enough.
> b/mm/hugetlb.c | 111 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
Is it worth deporking this for the CONFIG_NUMA=n case?
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