linux-kernel - [tip:sched/core] mm: Do not flush TLB during protection change if !pte_present && !migration

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Message-ID: <tip-e920e14ca29b0b2a981cfc90e4e20edd6f078d19@git.kernel.org>
Date:	Wed, 9 Oct 2013 10:25:32 -0700
From:	tip-bot for Mel Gorman <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	peterz@...radead.org, hannes@...xchg.org, riel@...hat.com,
	aarcange@...hat.com, srikar@...ux.vnet.ibm.com, mgorman@...e.de,
	tglx@...utronix.de
Subject: [tip:sched/core] mm:
  Do not flush TLB during protection change if !pte_present && !migration_entry

Commit-ID:  e920e14ca29b0b2a981cfc90e4e20edd6f078d19
Gitweb:     http://git.kernel.org/tip/e920e14ca29b0b2a981cfc90e4e20edd6f078d19
Author:     Mel Gorman <mgorman@...e.de>
AuthorDate: Mon, 7 Oct 2013 11:28:48 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 9 Oct 2013 12:39:48 +0200

mm: Do not flush TLB during protection change if !pte_present && !migration_entry

NUMA PTE scanning is expensive both in terms of the scanning itself and
the TLB flush if there are any updates. Currently non-present PTEs are
accounted for as an update and incurring a TLB flush where it is only
necessary for anonymous migration entries. This patch addresses the
problem and should reduce TLB flushes.

Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Reviewed-by: Rik van Riel <riel@...hat.com>
Signed-off-by: Mel Gorman <mgorman@...e.de>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-11-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 mm/mprotect.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/mprotect.c b/mm/mprotect.c
index 2bbb648..7bdbd4b 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -101,8 +101,9 @@ static unsigned long change_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 				make_migration_entry_read(&entry);
 				set_pte_at(mm, addr, pte,
 					swp_entry_to_pte(entry));
+
+				pages++;
 			}
-			pages++;
 		}
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 	arch_leave_lazy_mmu_mode();
--
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