Re: [PATCH v4 47/66] sched: Use maple tree iterator to walk VMAs

[Vlastimil Babka]

On 12/1/21 15:30, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
> 
> The linked list is slower than walking the VMAs using the maple tree.
> We can't use the VMA iterator here because it doesn't support
> moving to an earlier position.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>  kernel/sched/fair.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 6e476f6d9435..39bb4a6c8507 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2672,6 +2672,7 @@ static void task_numa_work(struct callback_head *work)
>  	struct task_struct *p = current;
>  	struct mm_struct *mm = p->mm;
>  	u64 runtime = p->se.sum_exec_runtime;
> +	MA_STATE(mas, &mm->mm_mt, 0, 0);
>  	struct vm_area_struct *vma;
>  	unsigned long start, end;
>  	unsigned long nr_pte_updates = 0;
> @@ -2728,13 +2729,16 @@ static void task_numa_work(struct callback_head *work)
>  
>  	if (!mmap_read_trylock(mm))
>  		return;
> -	vma = find_vma(mm, start);
> +	mas_set(&mas, start);
> +	vma = mas_find(&mas, ULONG_MAX);
>  	if (!vma) {
>  		reset_ptenuma_scan(p);
>  		start = 0;
> -		vma = mm->mmap;
> +		mas_set(&mas, start);
> +		vma = mas_find(&mas, ULONG_MAX);
>  	}
> -	for (; vma; vma = vma->vm_next) {
> +
> +	for (; vma; vma = mas_find(&mas, ULONG_MAX)) {
>  		if (!vma_migratable(vma) || !vma_policy_mof(vma) ||
>  			is_vm_hugetlb_page(vma) || (vma->vm_flags & VM_MIXEDMAP)) {
>  			continue;