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 <rientjes@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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 {
