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

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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>
This commit is contained in:
Mel Gorman 2013-10-07 11:28:48 +01:00 committed by Ingo Molnar
parent afcae2655b
commit e920e14ca2
1 changed files with 2 additions and 1 deletions
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3
mm/mprotect.c
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@ -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);