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Sun, 11 Jan 2026 04:19:46 -0800 (PST) From: Vernon Yang X-Google-Original-From: Vernon Yang To: akpm@linux-foundation.org, david@kernel.org Cc: lorenzo.stoakes@oracle.com, ziy@nvidia.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vernon Yang Subject: [PATCH mm-new v4 2/6] mm: khugepaged: refine scan progress number Date: Sun, 11 Jan 2026 20:19:05 +0800 Message-ID: <20260111121909.8410-3-yanglincheng@kylinos.cn> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260111121909.8410-1-yanglincheng@kylinos.cn> References: <20260111121909.8410-1-yanglincheng@kylinos.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, each scan always increases "progress" by HPAGE_PMD_NR, even if only scanning a single pte. This patch does not change the original semantics of "progress", it simply uses the exact number of PTEs counted to replace HPAGE_PMD_NR. Let me provide a detailed example: static int hpage_collapse_scan_pmd() { for (addr =3D start_addr, _pte =3D pte; _pte < pte + HPAGE_PMD_NR; _pte++, addr +=3D PAGE_SIZE) { pte_t pteval =3D ptep_get(_pte); ... if (pte_uffd_wp(pteval)) { <-- first scan hit result =3D SCAN_PTE_UFFD_WP; goto out_unmap; } } } During the first scan, if pte_uffd_wp(pteval) is true, the loop exits directly. In practice, only one PTE is scanned before termination. Here, "progress +=3D 1" reflects the actual number of PTEs scanned, but previously "progress +=3D HPAGE_PMD_NR" always. Signed-off-by: Vernon Yang Acked-by: David Hildenbrand (Red Hat) --- mm/khugepaged.c | 28 ++++++++++++++++++++++------ 1 file changed, 22 insertions(+), 6 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 2e570f83778c..5c6015ac7b5e 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1249,6 +1249,7 @@ static enum scan_result collapse_huge_page(struct mm_= struct *mm, unsigned long a static enum scan_result hpage_collapse_scan_pmd(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long start_addr, bool *mmap_locked, + int *cur_progress, struct collapse_control *cc) { pmd_t *pmd; @@ -1264,19 +1265,27 @@ static enum scan_result hpage_collapse_scan_pmd(str= uct mm_struct *mm, VM_BUG_ON(start_addr & ~HPAGE_PMD_MASK); =20 result =3D find_pmd_or_thp_or_none(mm, start_addr, &pmd); - if (result !=3D SCAN_SUCCEED) + if (result !=3D SCAN_SUCCEED) { + if (cur_progress) + *cur_progress =3D HPAGE_PMD_NR; goto out; + } =20 memset(cc->node_load, 0, sizeof(cc->node_load)); nodes_clear(cc->alloc_nmask); pte =3D pte_offset_map_lock(mm, pmd, start_addr, &ptl); if (!pte) { + if (cur_progress) + *cur_progress =3D HPAGE_PMD_NR; result =3D SCAN_NO_PTE_TABLE; goto out; } =20 for (addr =3D start_addr, _pte =3D pte; _pte < pte + HPAGE_PMD_NR; _pte++, addr +=3D PAGE_SIZE) { + if (cur_progress) + *cur_progress +=3D 1; + pte_t pteval =3D ptep_get(_pte); if (pte_none_or_zero(pteval)) { ++none_or_zero; @@ -2297,6 +2306,7 @@ static enum scan_result collapse_file(struct mm_struc= t *mm, unsigned long addr, =20 static enum scan_result hpage_collapse_scan_file(struct mm_struct *mm, uns= igned long addr, struct file *file, pgoff_t start, + int *cur_progress, struct collapse_control *cc) { struct folio *folio =3D NULL; @@ -2337,6 +2347,9 @@ static enum scan_result hpage_collapse_scan_file(stru= ct mm_struct *mm, unsigned continue; } =20 + if (cur_progress) + *cur_progress +=3D folio_nr_pages(folio); + if (folio_order(folio) =3D=3D HPAGE_PMD_ORDER && folio->index =3D=3D start) { /* Maybe PMD-mapped */ @@ -2466,6 +2479,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned = int pages, enum scan_result =20 while (khugepaged_scan.address < hend) { bool mmap_locked =3D true; + int cur_progress =3D 0; =20 cond_resched(); if (unlikely(hpage_collapse_test_exit_or_disable(mm))) @@ -2482,7 +2496,8 @@ static unsigned int khugepaged_scan_mm_slot(unsigned = int pages, enum scan_result mmap_read_unlock(mm); mmap_locked =3D false; *result =3D hpage_collapse_scan_file(mm, - khugepaged_scan.address, file, pgoff, cc); + khugepaged_scan.address, file, pgoff, + &cur_progress, cc); fput(file); if (*result =3D=3D SCAN_PTE_MAPPED_HUGEPAGE) { mmap_read_lock(mm); @@ -2496,7 +2511,8 @@ static unsigned int khugepaged_scan_mm_slot(unsigned = int pages, enum scan_result } } else { *result =3D hpage_collapse_scan_pmd(mm, vma, - khugepaged_scan.address, &mmap_locked, cc); + khugepaged_scan.address, &mmap_locked, + &cur_progress, cc); } =20 if (*result =3D=3D SCAN_SUCCEED) @@ -2504,7 +2520,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigned = int pages, enum scan_result =20 /* move to next address */ khugepaged_scan.address +=3D HPAGE_PMD_SIZE; - progress +=3D HPAGE_PMD_NR; + progress +=3D cur_progress; if (!mmap_locked) /* * We released mmap_lock so break loop. Note @@ -2826,11 +2842,11 @@ int madvise_collapse(struct vm_area_struct *vma, un= signed long start, mmap_read_unlock(mm); mmap_locked =3D false; result =3D hpage_collapse_scan_file(mm, addr, file, pgoff, - cc); + NULL, cc); fput(file); } else { result =3D hpage_collapse_scan_pmd(mm, vma, addr, - &mmap_locked, cc); + &mmap_locked, NULL, cc); } if (!mmap_locked) *lock_dropped =3D true; --=20 2.51.0