| Message ID | 20220809220100.20033-5-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: Remember a/d bits for migration entries | expand |
Peter Xu <peterx@redhat.com> writes: > Carry over the dirty bit from pmd to pte when a huge pmd splits. It > shouldn't be a correctness issue since when pmd_dirty() we'll have the page > marked dirty anyway, however having dirty bit carried over helps the next > initial writes of split ptes on some archs like x86. > > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > mm/huge_memory.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 0611b2fd145a..e8e78d1bac5f 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -2005,7 +2005,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > pgtable_t pgtable; > pmd_t old_pmd, _pmd; > bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; > - bool anon_exclusive = false; > + bool anon_exclusive = false, dirty = false; > unsigned long addr; > int i; > > @@ -2098,6 +2098,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > SetPageDirty(page); > write = pmd_write(old_pmd); > young = pmd_young(old_pmd); > + dirty = pmd_dirty(old_pmd); Nitpick: This can be put under if (pmd_dirty(old_pmd)) SetPageDirty(page); Not a big deal. Reviewed-by: "Huang, Ying" <ying.huang@intel.com> > soft_dirty = pmd_soft_dirty(old_pmd); > uffd_wp = pmd_uffd_wp(old_pmd); > > @@ -2161,6 +2162,9 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > entry = pte_wrprotect(entry); > if (!young) > entry = pte_mkold(entry); > + /* NOTE: this may set soft-dirty too on some archs */ > + if (dirty) > + entry = pte_mkdirty(entry); > if (soft_dirty) > entry = pte_mksoft_dirty(entry); > if (uffd_wp)
On Wed, Aug 10, 2022 at 02:24:33PM +0800, Huang, Ying wrote: > Peter Xu <peterx@redhat.com> writes: > > > Carry over the dirty bit from pmd to pte when a huge pmd splits. It > > shouldn't be a correctness issue since when pmd_dirty() we'll have the page > > marked dirty anyway, however having dirty bit carried over helps the next > > initial writes of split ptes on some archs like x86. > > > > Signed-off-by: Peter Xu <peterx@redhat.com> > > --- > > mm/huge_memory.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index 0611b2fd145a..e8e78d1bac5f 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -2005,7 +2005,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > > pgtable_t pgtable; > > pmd_t old_pmd, _pmd; > > bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; > > - bool anon_exclusive = false; > > + bool anon_exclusive = false, dirty = false; > > unsigned long addr; > > int i; > > > > @@ -2098,6 +2098,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > > SetPageDirty(page); > > write = pmd_write(old_pmd); > > young = pmd_young(old_pmd); > > + dirty = pmd_dirty(old_pmd); > > Nitpick: This can be put under > > if (pmd_dirty(old_pmd)) > SetPageDirty(page); > > Not a big deal. > > Reviewed-by: "Huang, Ying" <ying.huang@intel.com> Yeah will do, thanks.
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 0611b2fd145a..e8e78d1bac5f 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2005,7 +2005,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, pgtable_t pgtable; pmd_t old_pmd, _pmd; bool young, write, soft_dirty, pmd_migration = false, uffd_wp = false; - bool anon_exclusive = false; + bool anon_exclusive = false, dirty = false; unsigned long addr; int i; @@ -2098,6 +2098,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, SetPageDirty(page); write = pmd_write(old_pmd); young = pmd_young(old_pmd); + dirty = pmd_dirty(old_pmd); soft_dirty = pmd_soft_dirty(old_pmd); uffd_wp = pmd_uffd_wp(old_pmd); @@ -2161,6 +2162,9 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, entry = pte_wrprotect(entry); if (!young) entry = pte_mkold(entry); + /* NOTE: this may set soft-dirty too on some archs */ + if (dirty) + entry = pte_mkdirty(entry); if (soft_dirty) entry = pte_mksoft_dirty(entry); if (uffd_wp)
Carry over the dirty bit from pmd to pte when a huge pmd splits. It shouldn't be a correctness issue since when pmd_dirty() we'll have the page marked dirty anyway, however having dirty bit carried over helps the next initial writes of split ptes on some archs like x86. Signed-off-by: Peter Xu <peterx@redhat.com> --- mm/huge_memory.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)