Commit 6e97624d authored by Kefeng Wang's avatar Kefeng Wang Committed by Andrew Morton
Browse files

mm: mprotect: avoid unnecessary struct page accessing if pte_protnone() 

If the pte_protnone() is true, we could avoid unnecessary struct page
accessing and reduce cache footprint when scanning page tables for prot
numa, there was a similar change before, see more commit a818f536
("autonuma: reduce cache footprint when scanning page tables").

Link: https://lkml.kernel.org/r/20251023113737.3572790-3-wangkefeng.wang@huawei.com


Signed-off-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: default avatarZi Yan <ziy@nvidia.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarDev Jain <dev.jain@arm.com>
Reviewed-by: default avatarSidhartha Kumar <sidhartha.kumar@oracle.com>
Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 03aa8e4f

mm/mprotect.c

+13 −16
Original line number Diff line number Diff line
@@ -118,18 +118,13 @@ static int mprotect_folio_pte_batch(struct folio *folio, pte_t *ptep, 
	return folio_pte_batch_flags(folio, NULL, ptep, &pte, max_nr_ptes, flags);

}



static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr,

			   pte_t oldpte, pte_t *pte, int target_node,

static bool prot_numa_skip(struct vm_area_struct *vma, int target_node,

		struct folio *folio)

{

	bool ret = true;

	bool toptier;

	int nid;



	/* Avoid TLB flush if possible */

	if (pte_protnone(oldpte))

		goto skip;



	if (!folio)

		goto skip;
@@ -307,24 +302,26 @@ static long change_pte_range(struct mmu_gather *tlb, 
			struct page *page;

			pte_t ptent;



			/* Already in the desired state. */

			if (prot_numa && pte_protnone(oldpte))

				continue;



			page = vm_normal_page(vma, addr, oldpte);

			if (page)

				folio = page_folio(page);



			/*

			 * Avoid trapping faults against the zero or KSM

			 * pages. See similar comment in change_huge_pmd.

			 */

			if (prot_numa) {

				int ret = prot_numa_skip(vma, addr, oldpte, pte,

							 target_node, folio);

				if (ret) {

			if (prot_numa &&

			    prot_numa_skip(vma, target_node, folio)) {



				/* determine batch to skip */

				nr_ptes = mprotect_folio_pte_batch(folio,

					  pte, oldpte, max_nr_ptes, /* flags = */ 0);

				continue;

			}

			}



			nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, max_nr_ptes, flags);