The patch titled
Subject: mm, thp: avoid unlikely branches for split_huge_pmd
has been added to the -mm tree. Its filename is
mm-thp-avoid-unlikely-branches-for-split_huge_pmd.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-thp-avoid-unlikely-branches-for-split_huge_pmd.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-thp-avoid-unlikely-branches-for-split_huge_pmd.patch
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------------------------------------------------------
From: David Rientjes <rientjes@xxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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 -puN include/linux/huge_mm.h~mm-thp-avoid-unlikely-branches-for-split_huge_pmd include/linux/huge_mm.h
--- a/include/linux/huge_mm.h~mm-thp-avoid-unlikely-branches-for-split_huge_pmd
+++ a/include/linux/huge_mm.h
@@ -190,6 +190,8 @@ static inline void deferred_split_huge_p
#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 -puN mm/memory.c~mm-thp-avoid-unlikely-branches-for-split_huge_pmd mm/memory.c
--- a/mm/memory.c~mm-thp-avoid-unlikely-branches-for-split_huge_pmd
+++ a/mm/memory.c
@@ -1240,7 +1240,7 @@ static inline unsigned long zap_pmd_rang
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
/* 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 -puN mm/mempolicy.c~mm-thp-avoid-unlikely-branches-for-split_huge_pmd mm/mempolicy.c
--- a/mm/mempolicy.c~mm-thp-avoid-unlikely-branches-for-split_huge_pmd
+++ a/mm/mempolicy.c
@@ -496,7 +496,7 @@ static int queue_pages_pte_range(pmd_t *
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 -puN mm/mprotect.c~mm-thp-avoid-unlikely-branches-for-split_huge_pmd mm/mprotect.c
--- a/mm/mprotect.c~mm-thp-avoid-unlikely-branches-for-split_huge_pmd
+++ a/mm/mprotect.c
@@ -176,7 +176,7 @@ static inline unsigned long change_pmd_r
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 {
_
Patches currently in -mm which might be from rientjes@xxxxxxxxxx are
mm-thp-avoid-unlikely-branches-for-split_huge_pmd.patch
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