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mm: numa: Trap pmd hinting faults only if we would otherwise trap PTE faults

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Base page PMD faulting is meant to batch handle NUMA hinting faults from
PTEs. However, even is no PTE faults would ever be handled within a
range the kernel still traps PMD hinting faults. This patch avoids the
overhead.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-37-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Mel Gorman 2013-10-07 11:29:14 +01:00 committed by Ingo Molnar
parent 4591ce4f2d
commit 25cbbef192
1 changed files with 5 additions and 2 deletions
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7
mm/mprotect.c
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@ -146,6 +146,8 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
pmd = pmd_offset(pud, addr);
do {
unsigned long this_pages;
next = pmd_addr_end(addr, end);
if (pmd_trans_huge(*pmd)) {
if (next - addr != HPAGE_PMD_SIZE)
@ -165,8 +167,9 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
}
if (pmd_none_or_clear_bad(pmd))
continue;
pages += change_pte_range(vma, pmd, addr, next, newprot,
this_pages = change_pte_range(vma, pmd, addr, next, newprot,
dirty_accountable, prot_numa, &all_same_nidpid);
pages += this_pages;
/*
* If we are changing protections for NUMA hinting faults then
@ -174,7 +177,7 @@ static inline unsigned long change_pmd_range(struct vm_area_struct *vma,
* node. This allows a regular PMD to be handled as one fault
* and effectively batches the taking of the PTL
*/
if (prot_numa && all_same_nidpid)
if (prot_numa && this_pages && all_same_nidpid)
change_pmd_protnuma(vma->vm_mm, addr, pmd);
} while (pmd++, addr = next, addr != end);