Re: [PATCH v2] mm: hugetlb: optionally allocate gigantic hugepages using cma

From: Michal Hocko
Date: Tue Mar 10 2020 - 05:01:26 EST


On Mon 09-03-20 17:25:24, Roman Gushchin wrote:
[...]
> 2) Run-time allocations of gigantic hugepages are performed using the
> cma allocator and the dedicated cma area

[...]
> @@ -1237,6 +1246,23 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
> {
> unsigned long nr_pages = 1UL << huge_page_order(h);
>
> + if (IS_ENABLED(CONFIG_CMA) && hugetlb_cma[0]) {
> + struct page *page;
> + int nid;
> +
> + for_each_node_mask(nid, *nodemask) {
> + if (!hugetlb_cma[nid])
> + break;
> +
> + page = cma_alloc(hugetlb_cma[nid], nr_pages,
> + huge_page_order(h), true);
> + if (page)
> + return page;
> + }
> +
> + return NULL;

Is there any strong reason why the alloaction annot fallback to non-CMA
allocator when the cma is depleted?

> + }
> +
> return alloc_contig_pages(nr_pages, gfp_mask, nid, nodemask);
> }

--
Michal Hocko
SUSE Labs