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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@suse.de>
AuthorDate: Mon, 7 Oct 2013 11:28:48 +0100
Committer: Ingo Molnar <mingo@kernel.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@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-11-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.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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