2021-02-10 08:46:14

by Miaohe Lin

Subject: [PATCH] mm/hugetlb: remove redundant reservation check condition in alloc_huge_page()

If there is no reservation corresponding to a vma, map_chg is always != 0,
i.e. we can not meet the condition where a vma does not have reservation
while map_chg = 0.

Signed-off-by: Miaohe Lin <[email protected]>
---
mm/hugetlb.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 4f2c92ddbca4..36c3646fa55f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2311,7 +2311,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,

/* If this allocation is not consuming a reservation, charge it now.
*/
- deferred_reserve = map_chg || avoid_reserve || !vma_resv_map(vma);
+ deferred_reserve = map_chg || avoid_reserve;
if (deferred_reserve) {
ret = hugetlb_cgroup_charge_cgroup_rsvd(
idx, pages_per_huge_page(h), &h_cg);
--
2.19.1

2021-02-13 01:21:21

by Mike Kravetz

Subject: Re: [PATCH] mm/hugetlb: remove redundant reservation check condition in alloc_huge_page()

On 2/9/21 11:54 PM, Miaohe Lin wrote:
> If there is no reservation corresponding to a vma, map_chg is always != 0,
> i.e. we can not meet the condition where a vma does not have reservation
> while map_chg = 0.

This commit message might be easier to understand?

vma_resv_map(vma) checks if a reserve map is associated with the vma. The
routine vma_needs_reservation() will check vma_resv_map(vma) and return 1
if no reserv map is present. map_chg is set to the return value of
vma_needs_reservation(). Therefore, !vma_resv_map(vma) is redundant in the
expression:
map_chg || avoid_reserve || !vma_resv_map(vma);
Remove the redundant check.

--
Mike Kravetz

>
> Signed-off-by: Miaohe Lin <[email protected]>
> ---
> mm/hugetlb.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 4f2c92ddbca4..36c3646fa55f 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2311,7 +2311,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
>
> /* If this allocation is not consuming a reservation, charge it now.
> */
> - deferred_reserve = map_chg || avoid_reserve || !vma_resv_map(vma);
> + deferred_reserve = map_chg || avoid_reserve;
> if (deferred_reserve) {
> ret = hugetlb_cgroup_charge_cgroup_rsvd(
> idx, pages_per_huge_page(h), &h_cg);
>

2021-02-18 02:30:51

by Miaohe Lin

Subject: Re: [PATCH] mm/hugetlb: remove redundant reservation check condition in alloc_huge_page()

Hi:
On 2021/2/13 9:15, Mike Kravetz wrote:
> On 2/9/21 11:54 PM, Miaohe Lin wrote:
>> If there is no reservation corresponding to a vma, map_chg is always != 0,
>> i.e. we can not meet the condition where a vma does not have reservation
>> while map_chg = 0.
>
> This commit message might be easier to understand?
>
> vma_resv_map(vma) checks if a reserve map is associated with the vma. The
> routine vma_needs_reservation() will check vma_resv_map(vma) and return 1
> if no reserv map is present. map_chg is set to the return value of
> vma_needs_reservation(). Therefore, !vma_resv_map(vma) is redundant in the
> expression:
> map_chg || avoid_reserve || !vma_resv_map(vma);
> Remove the redundant check.
>

Sorry for late respond! I will use this wonderful commit message. Many thanks! :)