The patch titled
Subject: mm/cow: don't bother write protecting already write-protected huge pages
has been added to the -mm tree. Its filename is
mm-cow-dont-bother-write-protectig-already-write-protected-huge-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-cow-dont-bother-write-protectig-already-write-protected-huge-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-cow-dont-bother-write-protectig-already-write-protected-huge-pages.patch
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------------------------------------------------------
From: Nicholas Piggin <npiggin@xxxxxxxxx>
Subject: mm/cow: don't bother write protecting already write-protected huge pages
Patch series "mm: dirty/accessed pte optimisations".
This patch (of 3):
This is the THP equivalent for 1b2de5d039c8 ("mm/cow: don't bother write
protecting already write-protected pages").
Explicit hugetlb pages don't get the same treatment because they don't
appear to have the right accessor functions.
Link: http://lkml.kernel.org/r/20180828112034.30875-2-npiggin@xxxxxxxxx
Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
--- a/mm/huge_memory.c~mm-cow-dont-bother-write-protectig-already-write-protected-huge-pages
+++ a/mm/huge_memory.c
@@ -973,8 +973,11 @@ int copy_huge_pmd(struct mm_struct *dst_
mm_inc_nr_ptes(dst_mm);
pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
- pmdp_set_wrprotect(src_mm, addr, src_pmd);
- pmd = pmd_mkold(pmd_wrprotect(pmd));
+ if (pmd_write(pmd)) {
+ pmdp_set_wrprotect(src_mm, addr, src_pmd);
+ pmd = pmd_wrprotect(pmd);
+ }
+ pmd = pmd_mkold(pmd);
set_pmd_at(dst_mm, addr, dst_pmd, pmd);
ret = 0;
@@ -1064,8 +1067,11 @@ int copy_huge_pud(struct mm_struct *dst_
/* No huge zero pud yet */
}
- pudp_set_wrprotect(src_mm, addr, src_pud);
- pud = pud_mkold(pud_wrprotect(pud));
+ if (pud_write(pud)) {
+ pudp_set_wrprotect(src_mm, addr, src_pud);
+ pud = pud_wrprotect(pud);
+ }
+ pud = pud_mkold(pud);
set_pud_at(dst_mm, addr, dst_pud, pud);
ret = 0;
_
Patches currently in -mm which might be from npiggin@xxxxxxxxx are
mm-cow-dont-bother-write-protectig-already-write-protected-huge-pages.patch
mm-cow-optimise-pte-dirty-accessed-bits-handling-in-fork.patch
mm-optimise-pte-dirty-accessed-bit-setting-by-demand-based-pte-insertion.patch
