linux-kernel - Re: [PATCH v3] mm/khugepaged: sched to numa node when collapse huge page

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Date:   Wed, 27 Apr 2022 13:48:43 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Bibo Mao <maobibo@...ngson.cn>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        David Hildenbrand <david@...hat.com>,
        Yang Shi <shy828301@...il.com>
Subject: Re: [PATCH v3] mm/khugepaged: sched to numa node when collapse huge
 page

On Thu, 17 Mar 2022 02:50:24 -0400 Bibo Mao <maobibo@...ngson.cn> wrote:

> collapse huge page will copy huge page from general small pages,
> dest node is calculated from most one of source pages, however
> THP daemon is not scheduled on dest node. The performance may be
> poor since huge page copying across nodes, also cache is not used
> for target node. With this patch, khugepaged daemon switches to
> the same numa node with huge page. It saves copying time and makes
> use of local cache better.
> 
> With this patch, specint 2006 base performance is improved with 6%
> on Loongson 3C5000L platform with 32 cores and 8 numa nodes.
> 

Are there any acks for this one please?

> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -1066,6 +1066,7 @@ static void collapse_huge_page(struct mm_struct *mm,
>  	struct vm_area_struct *vma;
>  	struct mmu_notifier_range range;
>  	gfp_t gfp;
> +	const struct cpumask *cpumask;
>  
>  	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
>  
> @@ -1079,6 +1080,13 @@ static void collapse_huge_page(struct mm_struct *mm,
>  	 * that. We will recheck the vma after taking it again in write mode.
>  	 */
>  	mmap_read_unlock(mm);
> +
> +	/* sched to specified node before huage page memory copy */
> +	if (task_node(current) != node) {
> +		cpumask = cpumask_of_node(node);
> +		if (!cpumask_empty(cpumask))
> +			set_cpus_allowed_ptr(current, cpumask);
> +	}
>  	new_page = khugepaged_alloc_page(hpage, gfp, node);
>  	if (!new_page) {
>  		result = SCAN_ALLOC_HUGE_PAGE_FAIL;
> -- 
> 2.31.1
>