[PATCH v11 7/7] mm: Don't split THP page when syscall is called

Minchan Kim
2014-07-08T06:06:23Z

We don't need to split THP page when MADV_FREE syscall is
called. It could be done when VM decide really frees it so
we could avoid unnecessary THP split.

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
mm/madvise.c | 20 +++++++++++++++++++-
mm/rmap.c | 7 +++----
mm/vmscan.c | 28 ++++++++++++++++++----------
3 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index a6aa7d4c4e02..77f13a99584c 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -272,7 +272,25 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
pte_t *pte, ptent;
struct page *page;

- split_huge_page_pmd(vma, addr, pmd);
+ if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
+ struct page *page;
+ pmd_t orig_pmd;
+
+ orig_pmd = pmdp_get_and_clear(mm, addr, pmd);
+
+ /* No hugepage in swapcache */
+ page = pmd_page(orig_pmd);
+ VM_BUG_ON_PAGE(PageSwapCache(page), page);
+
+ orig_pmd = pmd_mkold(orig_pmd);
+ orig_pmd = pmd_mkclean(orig_pmd);
+
+ set_pmd_at(mm, addr, pmd, orig_pmd);
+ tlb_remove_pmd_tlb_entry(tlb, pmd, addr);
+ spin_unlock(ptl);
+ return 0;
+ }
+
if (pmd_trans_unstable(pmd))
return 0;

diff --git a/mm/rmap.c b/mm/rmap.c
index a8e34596dc97..67e1c1859c1d 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -703,10 +703,9 @@ static int page_referenced_one(struct page *page, struct vm_area_struct *vma,
if (pmdp_clear_flush_young_notify(vma, address, pmd))
referenced++;

- /*
- * In this implmentation, MADV_FREE doesn't support THP free
- */
- dirty++;
+ if (pmd_dirty(*pmd))
+ dirty++;
+
spin_unlock(ptl);
} else {
pte_t *pte;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index d88413ccadcc..6557f0b36321 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -971,17 +971,25 @@ static unsigned long shrink_page_list(struct list_head *page_list,
* Anonymous process memory has backing store?
* Try to allocate it some swap space here.
*/
- if (PageAnon(page) && !PageSwapCache(page) && !freeable) {
- if (!(sc->gfp_mask & __GFP_IO))
- goto keep_locked;
- if (!add_to_swap(page, page_list))
- goto activate_locked;
- may_enter_fs = 1;
-
- /* Adding to swap updated mapping */
- mapping = page_mapping(page);
+ if (PageAnon(page) && !PageSwapCache(page)) {
+ if (!freeable) {
+ if (!(sc->gfp_mask & __GFP_IO))
+ goto keep_locked;
+ if (!add_to_swap(page, page_list))
+ goto activate_locked;
+ may_enter_fs = 1;
+ /* Adding to swap updated mapping */
+ mapping = page_mapping(page);
+ } else {
+ if (likely(!PageTransHuge(page)))
+ goto unmap;
+ /* try_to_unmap isn't aware of THP page */
+ if (unlikely(split_huge_page_to_list(page,
+ page_list)))
+ goto keep_locked;
+ }
}
-
+unmap:
/*
* The page is mapped into the page tables of one or more
* processes. Try to unmap it here.
--
2.0.0