The patch titled
pagewalk: don't look up vma if walk->hugetlb_entry is unused
has been added to the -mm tree. Its filename is
pagewalk-dont-look-up-vma-if-walk-hugetlb_entry-is-unused.patch
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------------------------------------------------------
Subject: pagewalk: don't look up vma if walk->hugetlb_entry is unused
From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Currently, walk_page_range() calls find_vma() every page table for walk
iteration. but it's completely unnecessary if walk->hugetlb_entry is
unused. And we don't have to assume find_vma() is a lightweight
operation. So this patch checks the walk->hugetlb_entry and avoids the
find_vma() call if possible.
This patch also makes some cleanups. 1) remove ugly uninitialized_var()
and 2) #ifdef in function body.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@xxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Matt Mackall <mpm@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/pagewalk.c | 43 +++++++++++++++++++++++++++++++++++++------
1 file changed, 37 insertions(+), 6 deletions(-)
diff -puN mm/pagewalk.c~pagewalk-dont-look-up-vma-if-walk-hugetlb_entry-is-unused mm/pagewalk.c
--- a/mm/pagewalk.c~pagewalk-dont-look-up-vma-if-walk-hugetlb_entry-is-unused
+++ a/mm/pagewalk.c
@@ -126,7 +126,39 @@ static int walk_hugetlb_range(struct vm_
return 0;
}
-#endif
+
+static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
+{
+ struct vm_area_struct *vma;
+
+ /* We don't need vma lookup at all. */
+ if (!walk->hugetlb_entry)
+ return NULL;
+
+ VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
+ vma = find_vma(walk->mm, addr);
+ if (vma && vma->vm_start <= addr && is_vm_hugetlb_page(vma))
+ return vma;
+
+ return NULL;
+}
+
+#else /* CONFIG_HUGETLB_PAGE */
+static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
+{
+ return NULL;
+}
+
+static int walk_hugetlb_range(struct vm_area_struct *vma,
+ unsigned long addr, unsigned long end,
+ struct mm_walk *walk)
+{
+ return 0;
+}
+
+#endif /* CONFIG_HUGETLB_PAGE */
+
+
/**
* walk_page_range - walk a memory map's page tables with a callback
@@ -165,18 +197,17 @@ int walk_page_range(unsigned long addr,
pgd = pgd_offset(walk->mm, addr);
do {
- struct vm_area_struct *uninitialized_var(vma);
+ struct vm_area_struct *vma;
next = pgd_addr_end(addr, end);
-#ifdef CONFIG_HUGETLB_PAGE
/*
* handle hugetlb vma individually because pagetable walk for
* the hugetlb page is dependent on the architecture and
* we can't handled it in the same manner as non-huge pages.
*/
- vma = find_vma(walk->mm, addr);
- if (vma && vma->vm_start <= addr && is_vm_hugetlb_page(vma)) {
+ vma = hugetlb_vma(addr, walk);
+ if (vma) {
if (vma->vm_end < next)
next = vma->vm_end;
/*
@@ -189,7 +220,7 @@ int walk_page_range(unsigned long addr,
pgd = pgd_offset(walk->mm, next);
continue;
}
-#endif
+
if (pgd_none_or_clear_bad(pgd)) {
if (walk->pte_hole)
err = walk->pte_hole(addr, next, walk);
_
Patches currently in -mm which might be from kosaki.motohiro@xxxxxxxxxxxxxx are
vmscanmemcg-memcg-aware-swap-token.patch
vmscanmemcg-memcg-aware-swap-token-fix.patch
vmscanmemcg-memcg-aware-swap-token-fix-checkpatch-fixes.patch
vmscan-implement-swap-token-trace.patch
vmscan-implement-swap-token-priority-aging.patch
memcg-add-documentation-for-the-memorynumastat-api.patch
memcg-add-documentation-for-the-memorynumastat-api-fix.patch
mm-increase-reclaim_distance-to-30.patch
slab-use-numa_no_node.patch
mm-swap-token-fix-dead-link.patch
mm-swap-token-makes-global-variables-to-function-local.patch
mm-swap-token-add-a-comment-for-priority-aging.patch
pagewalk-fix-walk_page_range-dont-check-find_vma-result-properly.patch
pagewalk-dont-look-up-vma-if-walk-hugetlb_entry-is-unused.patch
pagewalk-add-locking-rule-comments.patch
pagewalk-add-locking-rule-comments-fix.patch
pagewalk-fix-code-comment-for-thp.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-fix-2.patch
cpusets-randomize-node-rotor-used-in-cpuset_mem_spread_node-cpusets-initialize-spread-rotor-lazily.patch
cpumask-convert-for_each_cpumask-with-for_each_cpu.patch
cpumask-alloc_cpumask_var-use-numa_no_node.patch
cpumask-add-cpumask_var_t-documentation.patch
kexec-remove-kmsg_dump_kexec.patch
kexec-remove-kmsg_dump_kexec-fix.patch
--
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