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

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Date:   Wed, 19 Jan 2022 17:49:54 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Liam Howlett <liam.howlett@...cle.com>,
        "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <walken.cr@...il.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Minchan Kim <minchan@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Rom Lemarchand <romlem@...gle.com>
Subject: Re: [PATCH v4 47/66] sched: Use maple tree iterator to walk VMAs

On 12/1/21 15:30, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> 
> 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@...radead.org>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  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;