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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 a818f5363a
("autonuma: reduce cache footprint when scanning page tables").

Link: https://lkml.kernel.org/r/20251023113737.3572790-3-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Acked-by: Zi Yan <ziy@nvidia.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Reviewed-by: Lorenzo 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kefeng Wang 2025-10-23 19:37:35 +08:00 committed by Andrew Morton
parent 03aa8e4f27
commit 6e97624dac
1 changed files with 13 additions and 16 deletions
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29
mm/mprotect.c
View File

@ -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); 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, static bool prot_numa_skip(struct vm_area_struct *vma, int target_node,
pte_t oldpte, pte_t *pte, int target_node, struct folio *folio)
struct folio *folio)
{ {
bool ret = true; bool ret = true;
bool toptier; bool toptier;
int nid; int nid;
/* Avoid TLB flush if possible */
if (pte_protnone(oldpte))
goto skip;
if (!folio) if (!folio)
goto skip; goto skip;
@ -307,23 +302,25 @@ static long change_pte_range(struct mmu_gather *tlb,
struct page *page; struct page *page;
pte_t ptent; pte_t ptent;
/* Already in the desired state. */
if (prot_numa && pte_protnone(oldpte))
continue;
page = vm_normal_page(vma, addr, oldpte); page = vm_normal_page(vma, addr, oldpte);
if (page) if (page)
folio = page_folio(page); folio = page_folio(page);
/* /*
* Avoid trapping faults against the zero or KSM * Avoid trapping faults against the zero or KSM
* pages. See similar comment in change_huge_pmd. * pages. See similar comment in change_huge_pmd.
*/ */
if (prot_numa) { if (prot_numa &&
int ret = prot_numa_skip(vma, addr, oldpte, pte, prot_numa_skip(vma, target_node, folio)) {
target_node, folio);
if (ret) {
/* determine batch to skip */ /* determine batch to skip */
nr_ptes = mprotect_folio_pte_batch(folio, nr_ptes = mprotect_folio_pte_batch(folio,
pte, oldpte, max_nr_ptes, /* flags = */ 0); pte, oldpte, max_nr_ptes, /* flags = */ 0);
continue; continue;
}
} }
nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, max_nr_ptes, flags); nr_ptes = mprotect_folio_pte_batch(folio, pte, oldpte, max_nr_ptes, flags);