linux-kernel - [RFC][PATCH 3/6] x86: mm: fix missed global TLB flush stat

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Message-Id: <20140218193012.4D308564@viggo.jf.intel.com>
Date:	Tue, 18 Feb 2014 11:30:12 -0800
From:	Dave Hansen <dave@...1.net>
To:	linux-kernel@...r.kernel.org
Cc:	linux-mm@...ck.org, ak@...ux.intel.com, alex.shi@...aro.org,
	kirill.shutemov@...ux.intel.com, mgorman@...e.de,
	tim.c.chen@...ux.intel.com, x86@...nel.org, peterz@...radead.org,
	Dave Hansen <dave@...1.net>
Subject: [RFC][PATCH 3/6] x86: mm: fix missed global TLB flush stat


From: Dave Hansen <dave.hansen@...ux.intel.com>

If we take the

	if (end == TLB_FLUSH_ALL || vmflag & VM_HUGETLB) {
		local_flush_tlb();
		goto out;
	}

path out of flush_tlb_mm_range(), we will have flushed the tlb,
but not incremented NR_TLB_LOCAL_FLUSH_ALL.  This unifies the
way out of the function so that we always take a single path when
doing a full tlb flush.

Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
---

 b/arch/x86/mm/tlb.c |   15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff -puN arch/x86/mm/tlb.c~fix-missed-global-flush-stat arch/x86/mm/tlb.c
--- a/arch/x86/mm/tlb.c~fix-missed-global-flush-stat	2014-02-18 10:59:37.611420354 -0800
+++ b/arch/x86/mm/tlb.c	2014-02-18 10:59:37.619420720 -0800
@@ -164,8 +164,9 @@ unsigned long tlb_single_page_flush_ceil
 void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
 				unsigned long end, unsigned long vmflag)
 {
-	int need_flush_others_all = 1;
 	unsigned long addr;
+	/* do a global flush by default */
+	unsigned long base_pages_to_flush = TLB_FLUSH_ALL;
 
 	preempt_disable();
 	if (current->active_mm != mm)
@@ -176,16 +177,14 @@ void flush_tlb_mm_range(struct mm_struct
 		goto out;
 	}
 
-	if (end == TLB_FLUSH_ALL || vmflag & VM_HUGETLB) {
-		local_flush_tlb();
-		goto out;
-	}
+	if ((end != TLB_FLUSH_ALL) && !(vmflag & VM_HUGETLB))
+		base_pages_to_flush = (end - start) >> PAGE_SHIFT;
 
-	if ((end - start) > tlb_single_page_flush_ceiling * PAGE_SIZE) {
+	if (base_pages_to_flush > tlb_single_page_flush_ceiling) {
+		base_pages_to_flush = TLB_FLUSH_ALL;
 		count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ALL);
 		local_flush_tlb();
 	} else {
-		need_flush_others_all = 0;
 		/* flush range by one by one 'invlpg' */
 		for (addr = start; addr < end;	addr += PAGE_SIZE) {
 			count_vm_tlb_event(NR_TLB_LOCAL_FLUSH_ONE);
@@ -193,7 +192,7 @@ void flush_tlb_mm_range(struct mm_struct
 		}
 	}
 out:
-	if (need_flush_others_all) {
+	if (base_pages_to_flush == TLB_FLUSH_ALL) {
 		start = 0UL;
 		end = TLB_FLUSH_ALL;
 	}
_
--
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