Subject: Re: [PATCH v2 2/4] mm: replace exec_folio_order() with generic preferred_exec_order()

From: Kiryl Shutsemau <[email-masked]>
Date: Fri, 20 Mar 2026 14:41:30 +0000

On Fri, Mar 20, 2026 at 06:58:52AM -0700, Usama Arif wrote:
> + *   allocations when memory is tight.
> + */
> +static unsigned int preferred_exec_order(struct vm_area_struct *vma)
> +{
> +	int order;
> +	unsigned long vma_len = vma_pages(vma);
> +	struct zone *zone;
> +	gfp_t gfp;
> +
> +	if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
> +		return 0;
> +
> +	/* Cap at min(PMD_ORDER, 2M) */
> +	order = min(HPAGE_PMD_ORDER, ilog2(SZ_2M >> PAGE_SHIFT));
> +
> +	/* Don't request folios larger than the VMA */
> +	order = min(order, ilog2(vma_len));
> +
> +	/* Step down under memory pressure */
> +	gfp = mapping_gfp_mask(vma->vm_file->f_mapping);
> +	zone = first_zones_zonelist(node_zonelist(numa_node_id(), gfp),
> +				    gfp_zone(gfp), NULL)->zone;
> +	if (zone) {
> +		while (order > 0 &&
> +		       !zone_watermark_ok(zone, order,
> +					  high_wmark_pages(zone), 0, 0))
> +			order--;
> +	}

Eww. That's overkill and layering violation.

If we need something like this, it has to be do within page allocator:
an allocation interface that takes a range (or mask) of acceptable
order.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov