Re: [PATCH v12 6/9] hugetlb_cgroup: support noreserve mappings

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