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SubjectRe: [PATCH v12 6/9] hugetlb_cgroup: support noreserve mappings
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On 2/11/20 1:31 PM, Mina Almasry wrote:
> Support MAP_NORESERVE accounting as part of the new counter.
>
> For each hugepage allocation, at allocation time we check if there is
> a reservation for this allocation or not. If there is a reservation for
> this allocation, then this allocation was charged at reservation time,
> and we don't re-account it. If there is no reserevation for this
> allocation, we charge the appropriate hugetlb_cgroup.
>
> The hugetlb_cgroup to uncharge for this allocation is stored in
> page[3].private. We use new APIs added in an earlier patch to set this
> pointer.
>
> Signed-off-by: Mina Almasry <almasrymina@google.com>
>
> ---
>
> Changes in v12:
> - Minor rebase to new interface for readability.
>
> Changes in v10:
> - Refactored deferred_reserve check.
>
> ---
> mm/hugetlb.c | 27 ++++++++++++++++++++++++++-
> 1 file changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index a9171c3cbed6b..2d62dd35399db 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1342,6 +1342,8 @@ static void __free_huge_page(struct page *page)
> clear_page_huge_active(page);
> hugetlb_cgroup_uncharge_page(hstate_index(h),
> pages_per_huge_page(h), page);
> + hugetlb_cgroup_uncharge_page_rsvd(hstate_index(h),
> + pages_per_huge_page(h), page);
> if (restore_reserve)
> h->resv_huge_pages++;
>
> @@ -2175,6 +2177,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
> long gbl_chg;
> int ret, idx;
> struct hugetlb_cgroup *h_cg;
> + bool deferred_reserve;
>
> idx = hstate_index(h);
> /*
> @@ -2212,9 +2215,19 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
> gbl_chg = 1;
> }
>
> + /* If this allocation is not consuming a reservation, charge it now.
> + */
> + deferred_reserve = map_chg || avoid_reserve || !vma_resv_map(vma);
> + if (deferred_reserve) {
> + ret = hugetlb_cgroup_charge_cgroup_rsvd(
> + idx, pages_per_huge_page(h), &h_cg);
> + if (ret)
> + goto out_subpool_put;
> + }
> +
> ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
> if (ret)
> - goto out_subpool_put;
> + goto out_uncharge_cgroup_reservation;
>
> spin_lock(&hugetlb_lock);
> /*
> @@ -2237,6 +2250,14 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
> /* Fall through */
> }
> hugetlb_cgroup_commit_charge(idx, pages_per_huge_page(h), h_cg, page);
> + /* If allocation is not consuming a reservation, also store the
> + * hugetlb_cgroup pointer on the page.
> + */
> + if (deferred_reserve) {
> + hugetlb_cgroup_commit_charge_rsvd(idx, pages_per_huge_page(h),
> + h_cg, page);
> + }
> +

This started before your new code, but those two cgroup_commit_charge calls
could/should be done outside the hugetlb_lock. No need to change as it is
not a big deal. Those calls only set fields in the page structs.

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

--
Mike Kravetz

> spin_unlock(&hugetlb_lock);
>
> set_page_private(page, (unsigned long)spool);
> @@ -2261,6 +2282,10 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
>
> out_uncharge_cgroup:
> hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), h_cg);
> +out_uncharge_cgroup_reservation:
> + if (deferred_reserve)
> + hugetlb_cgroup_uncharge_cgroup_rsvd(idx, pages_per_huge_page(h),
> + h_cg);
> out_subpool_put:
> if (map_chg || avoid_reserve)
> hugepage_subpool_put_pages(spool, 1);
> --
> 2.25.0.225.g125e21ebc7-goog
>

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