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Commit 25cbbef1 authored by Mel Gorman's avatar Mel Gorman Committed by Ingo Molnar
Browse files

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



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: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarRik 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: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-37-git-send-email-mgorman@suse.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 4591ce4f

mm/mprotect.c

+5 −2
Original line number Diff line number Diff line
@@ -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);