linux-kernel - [PATCH 1/7] mm/pagewalk: remove pgd_entry() and pud

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Date:	Fri,  6 Jun 2014 18:58:34 -0400
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	linux-mm@...ck.org
Cc:	Dave Hansen <dave.hansen@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/7] mm/pagewalk: remove pgd_entry() and pud_entry()

Currently no user of page table walker sets ->pgd_entry() or ->pud_entry(),
so checking their existence in each loop is just wasting CPU cycle.
So let's remove it to reduce overhead.

Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
---
 include/linux/mm.h |  6 ------
 mm/pagewalk.c      | 18 +-----------------
 2 files changed, 1 insertion(+), 23 deletions(-)

diff --git v3.15-rc8-mmots-2014-06-03-16-28.orig/include/linux/mm.h v3.15-rc8-mmots-2014-06-03-16-28/include/linux/mm.h
index 563c79ea07bd..b4aa6579f2b1 100644
--- v3.15-rc8-mmots-2014-06-03-16-28.orig/include/linux/mm.h
+++ v3.15-rc8-mmots-2014-06-03-16-28/include/linux/mm.h
@@ -1092,8 +1092,6 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
 
 /**
  * mm_walk - callbacks for walk_page_range
- * @pgd_entry: if set, called for each non-empty PGD (top-level) entry
- * @pud_entry: if set, called for each non-empty PUD (2nd-level) entry
  * @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
  *	       this handler is required to be able to handle
  *	       pmd_trans_huge() pmds.  They may simply choose to
@@ -1115,10 +1113,6 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
  * (see the comment on walk_page_range() for more details)
  */
 struct mm_walk {
-	int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
-			 unsigned long next, struct mm_walk *walk);
-	int (*pud_entry)(pud_t *pud, unsigned long addr,
-	                 unsigned long next, struct mm_walk *walk);
 	int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
 			 unsigned long next, struct mm_walk *walk);
 	int (*pte_entry)(pte_t *pte, unsigned long addr,
diff --git v3.15-rc8-mmots-2014-06-03-16-28.orig/mm/pagewalk.c v3.15-rc8-mmots-2014-06-03-16-28/mm/pagewalk.c
index b2a075ffb96e..15c7585e8684 100644
--- v3.15-rc8-mmots-2014-06-03-16-28.orig/mm/pagewalk.c
+++ v3.15-rc8-mmots-2014-06-03-16-28/mm/pagewalk.c
@@ -115,14 +115,6 @@ static int walk_pud_range(pgd_t *pgd, unsigned long addr,
 			continue;
 		}
 
-		if (walk->pud_entry) {
-			err = walk->pud_entry(pud, addr, next, walk);
-			if (skip_lower_level_walking(walk))
-				continue;
-			if (err)
-				break;
-		}
-
 		if (walk->pmd_entry || walk->pte_entry) {
 			err = walk_pmd_range(pud, addr, next, walk);
 			if (err)
@@ -152,15 +144,7 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
 			continue;
 		}
 
-		if (walk->pgd_entry) {
-			err = walk->pgd_entry(pgd, addr, next, walk);
-			if (skip_lower_level_walking(walk))
-				continue;
-			if (err)
-				break;
-		}
-
-		if (walk->pud_entry || walk->pmd_entry || walk->pte_entry) {
+		if (walk->pmd_entry || walk->pte_entry) {
 			err = walk_pud_range(pgd, addr, next, walk);
 			if (err)
 				break;
-- 
1.9.3

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