linux-kernel - [PATCH 1/2] Revert "mm: make faultaround produce old ptes"

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Date:	Tue, 14 Jun 2016 11:42:29 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	"Huang, Ying" <ying.huang@...el.com>,
	Michal Hocko <mhocko@...e.com>,
	Minchan Kim <minchan@...nel.org>,
	Vinayak Menon <vinmenon@...eaurora.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH 1/2] Revert "mm: make faultaround produce old ptes"

This reverts commit 5c0a85fad949212b3e059692deecdeed74ae7ec7.

The commit causes ~6% regression in unixbench.

Let's revert it for now and consider other solution for reclaim problem
later.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reported-by: "Huang, Ying" <ying.huang@...el.com>
---
 include/linux/mm.h |  2 +-
 mm/filemap.c       |  2 +-
 mm/memory.c        | 23 +++++------------------
 3 files changed, 7 insertions(+), 20 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5df5feb49575..ece042dfe23c 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -602,7 +602,7 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
 }
 
 void do_set_pte(struct vm_area_struct *vma, unsigned long address,
-		struct page *page, pte_t *pte, bool write, bool anon, bool old);
+		struct page *page, pte_t *pte, bool write, bool anon);
 #endif
 
 /*
diff --git a/mm/filemap.c b/mm/filemap.c
index 00ae878b2a38..20f3b1f33f0e 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2186,7 +2186,7 @@ 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, true);
+		do_set_pte(vma, addr, page, pte, false, false);
 		unlock_page(page);
 		goto next;
 unlock:
diff --git a/mm/memory.c b/mm/memory.c
index 15322b73636b..61fe7e7b56bf 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2877,7 +2877,7 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address,
  * 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, bool old)
+		struct page *page, pte_t *pte, bool write, bool anon)
 {
 	pte_t entry;
 
@@ -2885,8 +2885,6 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address,
 	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);
@@ -3032,20 +3030,9 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 	 */
 	if (vma->vm_ops->map_pages && fault_around_bytes >> PAGE_SHIFT > 1) {
 		pte = pte_offset_map_lock(mm, pmd, address, &ptl);
-		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);
+		if (!pte_same(*pte, orig_pte))
 			goto unlock_out;
-		}
 		pte_unmap_unlock(pte, ptl);
 	}
 
@@ -3060,7 +3047,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		put_page(fault_page);
 		return ret;
 	}
-	do_set_pte(vma, address, fault_page, pte, false, false, false);
+	do_set_pte(vma, address, fault_page, pte, false, false);
 	unlock_page(fault_page);
 unlock_out:
 	pte_unmap_unlock(pte, ptl);
@@ -3111,7 +3098,7 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		}
 		goto uncharge_out;
 	}
-	do_set_pte(vma, address, new_page, pte, true, true, false);
+	do_set_pte(vma, address, new_page, pte, true, true);
 	mem_cgroup_commit_charge(new_page, memcg, false, false);
 	lru_cache_add_active_or_unevictable(new_page, vma);
 	pte_unmap_unlock(pte, ptl);
@@ -3164,7 +3151,7 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		put_page(fault_page);
 		return ret;
 	}
-	do_set_pte(vma, address, fault_page, pte, true, false, false);
+	do_set_pte(vma, address, fault_page, pte, true, false);
 	pte_unmap_unlock(pte, ptl);
 
 	if (set_page_dirty(fault_page))
-- 
2.8.1