The patch titled
Subject: mm: make faultaround produce old ptes
has been added to the -mm tree. Its filename is
mm-make-faultaround-produce-old-ptes.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-make-faultaround-produce-old-ptes.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-make-faultaround-produce-old-ptes.patch
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From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: mm: make faultaround produce old ptes
Currently, faultaround code produces young pte. This can screw up vmscan
behaviour[1], as it makes vmscan think that these pages are hot and not
push them out on first round.
Modify faultaround to produce old ptes, so they can easily be reclaimed
under memory pressure.
This can to some extend defeat the purpose of faultaround on machines
without hardware accessed bit as it will not help us with reducing the
number of minor page faults.
We may want to disable faultaround on such machines altogether, but that's
subject for separate patchset.
[1] https://lkml.kernel.org/r/1460992636-711-1-git-send-email-vinmenon@xxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1463488366-47723-1-git-send-email-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vinayak Menon <vinmenon@xxxxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mm.h | 2 +-
mm/filemap.c | 2 +-
mm/memory.c | 23 ++++++++++++++++++-----
3 files changed, 20 insertions(+), 7 deletions(-)
diff -puN include/linux/mm.h~mm-make-faultaround-produce-old-ptes include/linux/mm.h
--- a/include/linux/mm.h~mm-make-faultaround-produce-old-ptes
+++ a/include/linux/mm.h
@@ -596,7 +596,7 @@ static inline pte_t maybe_mkwrite(pte_t
}
void do_set_pte(struct vm_area_struct *vma, unsigned long address,
- struct page *page, pte_t *pte, bool write, bool anon);
+ struct page *page, pte_t *pte, bool write, bool anon, bool old);
#endif
/*
diff -puN mm/filemap.c~mm-make-faultaround-produce-old-ptes mm/filemap.c
--- a/mm/filemap.c~mm-make-faultaround-produce-old-ptes
+++ a/mm/filemap.c
@@ -2193,7 +2193,7 @@ repeat:
if (file->f_ra.mmap_miss > 0)
file->f_ra.mmap_miss--;
addr = address + (page->index - vmf->pgoff) * PAGE_SIZE;
- do_set_pte(vma, addr, page, pte, false, false);
+ do_set_pte(vma, addr, page, pte, false, false, true);
unlock_page(page);
goto next;
unlock:
diff -puN mm/memory.c~mm-make-faultaround-produce-old-ptes mm/memory.c
--- a/mm/memory.c~mm-make-faultaround-produce-old-ptes
+++ a/mm/memory.c
@@ -2876,7 +2876,7 @@ static int __do_fault(struct vm_area_str
* vm_ops->map_pages.
*/
void do_set_pte(struct vm_area_struct *vma, unsigned long address,
- struct page *page, pte_t *pte, bool write, bool anon)
+ struct page *page, pte_t *pte, bool write, bool anon, bool old)
{
pte_t entry;
@@ -2884,6 +2884,8 @@ void do_set_pte(struct vm_area_struct *v
entry = mk_pte(page, vma->vm_page_prot);
if (write)
entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+ if (old)
+ entry = pte_mkold(entry);
if (anon) {
inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
page_add_new_anon_rmap(page, vma, address, false);
@@ -3021,9 +3023,20 @@ static int do_read_fault(struct mm_struc
*/
if (vma->vm_ops->map_pages && fault_around_bytes >> PAGE_SHIFT > 1) {
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
- do_fault_around(vma, address, pte, pgoff, flags);
if (!pte_same(*pte, orig_pte))
goto unlock_out;
+ do_fault_around(vma, address, pte, pgoff, flags);
+ /* Check if the fault is handled by faultaround */
+ if (!pte_same(*pte, orig_pte)) {
+ /*
+ * Faultaround produce old pte, but the pte we've
+ * handler fault for should be young.
+ */
+ pte_t entry = pte_mkyoung(*pte);
+ if (ptep_set_access_flags(vma, address, pte, entry, 0))
+ update_mmu_cache(vma, address, pte);
+ goto unlock_out;
+ }
pte_unmap_unlock(pte, ptl);
}
@@ -3038,7 +3051,7 @@ static int do_read_fault(struct mm_struc
put_page(fault_page);
return ret;
}
- do_set_pte(vma, address, fault_page, pte, false, false);
+ do_set_pte(vma, address, fault_page, pte, false, false, false);
unlock_page(fault_page);
unlock_out:
pte_unmap_unlock(pte, ptl);
@@ -3090,7 +3103,7 @@ static int do_cow_fault(struct mm_struct
}
goto uncharge_out;
}
- do_set_pte(vma, address, new_page, pte, true, true);
+ do_set_pte(vma, address, new_page, pte, true, true, false);
mem_cgroup_commit_charge(new_page, memcg, false, false);
lru_cache_add_active_or_unevictable(new_page, vma);
pte_unmap_unlock(pte, ptl);
@@ -3147,7 +3160,7 @@ static int do_shared_fault(struct mm_str
put_page(fault_page);
return ret;
}
- do_set_pte(vma, address, fault_page, pte, true, false);
+ do_set_pte(vma, address, fault_page, pte, true, false, false);
pte_unmap_unlock(pte, ptl);
if (set_page_dirty(fault_page))
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
mm-make-faultaround-produce-old-ptes.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix-2.patch
mm-make-swapin-readahead-to-improve-thp-collapse-rate-fix-3.patch
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