From fd60775aea802beef444881ddfa111a4b73b1bbc Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Mon, 12 Dec 2016 16:42:20 -0800 Subject: [PATCH] mm, thp: avoid unlikely branches for split_huge_pmd While doing MADV_DONTNEED on a large area of thp memory, I noticed we encountered many unlikely() branches in profiles for each backing hugepage. This is because zap_pmd_range() would call split_huge_pmd(), which rechecked the conditions that were already validated, but as part of an unlikely() branch. Avoid the unlikely() branch when in a context where pmd is known to be good for __split_huge_pmd() directly. Link: http://lkml.kernel.org/r/alpine.DEB.2.10.1610181600300.84525@chino.kir.corp.google.com Signed-off-by: David Rientjes Acked-by: Vlastimil Babka Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/huge_mm.h | 2 ++ mm/memory.c | 4 ++-- mm/mempolicy.c | 2 +- mm/mprotect.c | 2 +- 4 files changed, 6 insertions(+), 4 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index e35e6de..1f782aa 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -189,6 +189,8 @@ static inline void deferred_split_huge_page(struct page *page) {} #define split_huge_pmd(__vma, __pmd, __address) \ do { } while (0) +static inline void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, + unsigned long address, bool freeze, struct page *page) {} static inline void split_huge_pmd_address(struct vm_area_struct *vma, unsigned long address, bool freeze, struct page *page) {} diff --git a/mm/memory.c b/mm/memory.c index 33f45ed..d86b7b4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1240,7 +1240,7 @@ static inline unsigned long zap_pmd_range(struct mmu_gather *tlb, if (next - addr != HPAGE_PMD_SIZE) { VM_BUG_ON_VMA(vma_is_anonymous(vma) && !rwsem_is_locked(&tlb->mm->mmap_sem), vma); - split_huge_pmd(vma, pmd, addr); + __split_huge_pmd(vma, pmd, addr, false, NULL); } else if (zap_huge_pmd(tlb, vma, pmd, addr)) goto next; /* fall through */ @@ -3454,7 +3454,7 @@ static int wp_huge_pmd(struct fault_env *fe, pmd_t orig_pmd) /* COW handled on pte level: split pmd */ VM_BUG_ON_VMA(fe->vma->vm_flags & VM_SHARED, fe->vma); - split_huge_pmd(fe->vma, fe->pmd, fe->address); + __split_huge_pmd(fe->vma, fe->pmd, fe->address, false, NULL); return VM_FAULT_FALLBACK; } diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 0b859af..a6a27e5 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -496,7 +496,7 @@ static int queue_pages_pte_range(pmd_t *pmd, unsigned long addr, page = pmd_page(*pmd); if (is_huge_zero_page(page)) { spin_unlock(ptl); - split_huge_pmd(vma, pmd, addr); + __split_huge_pmd(vma, pmd, addr, false, NULL); } else { get_page(page); spin_unlock(ptl); diff --git a/mm/mprotect.c b/mm/mprotect.c index 05a02b7..c5ba2aa 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -176,7 +176,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma, if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd)) { if (next - addr != HPAGE_PMD_SIZE) { - split_huge_pmd(vma, pmd, addr); + __split_huge_pmd(vma, pmd, addr, false, NULL); if (pmd_trans_unstable(pmd)) continue; } else { -- 2.7.4