Commit e920e14c authored Oct 07, 2013 by Mel Gorman Committed by Ingo Molnar Oct 09, 2013

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>

parent afcae265

mm/mprotect.c

+2 −1

Original line number	Diff line number	Diff line
		@@ -101,9 +101,10 @@ 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++;
		}
		}
		} while (pte++, addr += PAGE_SIZE, addr != end);
		arch_leave_lazy_mmu_mode();
		pte_unmap_unlock(pte - 1, ptl);