From: Lance Yang ioworker0@gmail.com
mainline inclusion from mainline-v6.10-rc1 commit 1b68112c40395b3b0fed3c8bb648e2d9d0b37ec2 category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/IAIHQO
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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Patch series "mm/madvise: enhance lazyfreeing with mTHP in madvise_free", v10.
This patchset adds support for lazyfreeing multi-size THP (mTHP) without needing to first split the large folio via split_folio(). However, we still need to split a large folio that is not fully mapped within the target range.
If a large folio is locked or shared, or if we fail to split it, we just leave it in place and advance to the next PTE in the range. But note that the behavior is changed; previously, any failure of this sort would cause the entire operation to give up. As large folios become more common, sticking to the old way could result in wasted opportunities.
Performance Testing ===================
On an Intel I5 CPU, lazyfreeing a 1GiB VMA backed by PTE-mapped folios of the same size results in the following runtimes for madvise(MADV_FREE) in seconds (shorter is better):
Folio Size | Old | New | Change ------------------------------------------ 4KiB | 0.590251 | 0.590259 | 0% 16KiB | 2.990447 | 0.185655 | -94% 32KiB | 2.547831 | 0.104870 | -95% 64KiB | 2.457796 | 0.052812 | -97% 128KiB | 2.281034 | 0.032777 | -99% 256KiB | 2.230387 | 0.017496 | -99% 512KiB | 2.189106 | 0.010781 | -99% 1024KiB | 2.183949 | 0.007753 | -99% 2048KiB | 0.002799 | 0.002804 | 0%
This patch (of 4):
This commit introduces clear_young_dirty_ptes() to replace mkold_ptes(). By doing so, we can use the same function for both use cases (madvise_pageout and madvise_free), and it also provides the flexibility to only clear the dirty flag in the future if needed.
Link: https://lkml.kernel.org/r/20240418134435.6092-1-ioworker0@gmail.com Link: https://lkml.kernel.org/r/20240418134435.6092-2-ioworker0@gmail.com Signed-off-by: Lance Yang ioworker0@gmail.com Suggested-by: Ryan Roberts ryan.roberts@arm.com Acked-by: David Hildenbrand david@redhat.com Reviewed-by: Ryan Roberts ryan.roberts@arm.com Cc: Barry Song 21cnbao@gmail.com Cc: Jeff Xie xiehuan09@gmail.com Cc: Kefeng Wang wangkefeng.wang@huawei.com Cc: Michal Hocko mhocko@suse.com Cc: Minchan Kim minchan@kernel.org Cc: Muchun Song songmuchun@bytedance.com Cc: Peter Xu peterx@redhat.com Cc: Yang Shi shy828301@gmail.com Cc: Yin Fengwei fengwei.yin@intel.com Cc: Zach O'Keefe zokeefe@google.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Liu Shixin liushixin2@huawei.com --- include/linux/mm_types.h | 9 +++++ include/linux/pgtable.h | 74 ++++++++++++++++++++++++---------------- mm/madvise.c | 3 +- 3 files changed, 55 insertions(+), 31 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index b99610d53256..6d6a2f090eef 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -1346,6 +1346,15 @@ enum fault_flag {
typedef unsigned int __bitwise zap_flags_t;
+/* Flags for clear_young_dirty_ptes(). */ +typedef int __bitwise cydp_t; + +/* Clear the access bit */ +#define CYDP_CLEAR_YOUNG ((__force cydp_t)BIT(0)) + +/* Clear the dirty bit */ +#define CYDP_CLEAR_DIRTY ((__force cydp_t)BIT(1)) + /* * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each * other. Here is what they mean, and how to use them: diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index d96927423a08..2ac8e48031cb 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -335,36 +335,6 @@ static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, } #endif
-#ifndef mkold_ptes -/** - * mkold_ptes - Mark PTEs that map consecutive pages of the same folio as old. - * @vma: VMA the pages are mapped into. - * @addr: Address the first page is mapped at. - * @ptep: Page table pointer for the first entry. - * @nr: Number of entries to mark old. - * - * May be overridden by the architecture; otherwise, implemented as a simple - * loop over ptep_test_and_clear_young(). - * - * Note that PTE bits in the PTE range besides the PFN can differ. For example, - * some PTEs might be write-protected. - * - * Context: The caller holds the page table lock. The PTEs map consecutive - * pages that belong to the same folio. The PTEs are all in the same PMD. - */ -static inline void mkold_ptes(struct vm_area_struct *vma, unsigned long addr, - pte_t *ptep, unsigned int nr) -{ - for (;;) { - ptep_test_and_clear_young(vma, addr, ptep); - if (--nr == 0) - break; - ptep++; - addr += PAGE_SIZE; - } -} -#endif - #ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_ARCH_HAS_NONLEAF_PMD_YOUNG) static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma, @@ -475,6 +445,50 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, } #endif
+#ifndef clear_young_dirty_ptes +/** + * clear_young_dirty_ptes - Mark PTEs that map consecutive pages of the + * same folio as old/clean. + * @mm: Address space the pages are mapped into. + * @addr: Address the first page is mapped at. + * @ptep: Page table pointer for the first entry. + * @nr: Number of entries to mark old/clean. + * @flags: Flags to modify the PTE batch semantics. + * + * May be overridden by the architecture; otherwise, implemented by + * get_and_clear/modify/set for each pte in the range. + * + * Note that PTE bits in the PTE range besides the PFN can differ. For example, + * some PTEs might be write-protected. + * + * Context: The caller holds the page table lock. The PTEs map consecutive + * pages that belong to the same folio. The PTEs are all in the same PMD. + */ +static inline void clear_young_dirty_ptes(struct vm_area_struct *vma, + unsigned long addr, pte_t *ptep, + unsigned int nr, cydp_t flags) +{ + pte_t pte; + + for (;;) { + if (flags == CYDP_CLEAR_YOUNG) + ptep_test_and_clear_young(vma, addr, ptep); + else { + pte = ptep_get_and_clear(vma->vm_mm, addr, ptep); + if (flags & CYDP_CLEAR_YOUNG) + pte = pte_mkold(pte); + if (flags & CYDP_CLEAR_DIRTY) + pte = pte_mkclean(pte); + set_pte_at(vma->vm_mm, addr, ptep, pte); + } + if (--nr == 0) + break; + ptep++; + addr += PAGE_SIZE; + } +} +#endif + static inline void ptep_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep) { diff --git a/mm/madvise.c b/mm/madvise.c index a38bcdf335f6..674f7402a8bb 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -551,7 +551,8 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd, continue;
if (!pageout && pte_young(ptent)) { - mkold_ptes(vma, addr, pte, nr); + clear_young_dirty_ptes(vma, addr, pte, nr, + CYDP_CLEAR_YOUNG); tlb_remove_tlb_entries(tlb, pte, nr, addr); }