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Commit 12ebc158 authored by Vineet Gupta's avatar Vineet Gupta
Browse files

mm,thp: introduce flush_pmd_tlb_range 



ARCHes with special requirements for evicting THP backing TLB entries
can implement this.

Otherwise also, it can help optimize TLB flush in THP regime.
stock flush_tlb_range() typically has optimization to nuke the entire
TLB if flush span is greater than a certain threshhold, which will
likely be true for a single huge page. Thus a single thp flush will
invalidate the entrire TLB which is not desirable.

e.g. see arch/arc: flush_pmd_tlb_range

Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: http://lkml.kernel.org/r/20151009100816.GC7873@node


Signed-off-by: default avatarVineet Gupta <vgupta@synopsys.com>
parent bd5e88ad

mm/huge_memory.c

+1 −1
Original line number Diff line number Diff line
@@ -1880,7 +1880,7 @@ static int __split_huge_page_map(struct page *page, 
		 * here). But it is generally safer to never allow

		 * small and huge TLB entries for the same virtual

		 * address to be loaded simultaneously. So instead of

		 * doing "pmd_populate(); flush_tlb_range();" we first

		 * doing "pmd_populate(); flush_pmd_tlb_range();" we first

		 * mark the current pmd notpresent (atomically because

		 * here the pmd_trans_huge and pmd_trans_splitting

		 * must remain set at all times on the pmd until the

mm/pgtable-generic.c

+20 −6
Original line number Diff line number Diff line
@@ -84,6 +84,20 @@ pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address, 


#ifdef CONFIG_TRANSPARENT_HUGEPAGE



#ifndef __HAVE_ARCH_FLUSH_PMD_TLB_RANGE



/*

 * ARCHes with special requirements for evicting THP backing TLB entries can

 * implement this. Otherwise also, it can help optimize normal TLB flush in

 * THP regime. stock flush_tlb_range() typically has optimization to nuke the

 * entire TLB TLB if flush span is greater than a threshhold, which will

 * likely be true for a single huge page. Thus a single thp flush will

 * invalidate the entire TLB which is not desitable.

 * e.g. see arch/arc: flush_pmd_tlb_range

 */

#define flush_pmd_tlb_range(vma, addr, end)	flush_tlb_range(vma, addr, end)

#endif



#ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS

int pmdp_set_access_flags(struct vm_area_struct *vma,

			  unsigned long address, pmd_t *pmdp,
@@ -93,7 +107,7 @@ int pmdp_set_access_flags(struct vm_area_struct *vma, 
	VM_BUG_ON(address & ~HPAGE_PMD_MASK);

	if (changed) {

		set_pmd_at(vma->vm_mm, address, pmdp, entry);

		flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

		flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

	}

	return changed;

}
@@ -107,7 +121,7 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma, 
	VM_BUG_ON(address & ~HPAGE_PMD_MASK);

	young = pmdp_test_and_clear_young(vma, address, pmdp);

	if (young)

		flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

		flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

	return young;

}

#endif
@@ -120,7 +134,7 @@ pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address, 
	VM_BUG_ON(address & ~HPAGE_PMD_MASK);

	VM_BUG_ON(!pmd_trans_huge(*pmdp));

	pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);

	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

	flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

	return pmd;

}

#endif
@@ -133,7 +147,7 @@ void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address, 
	VM_BUG_ON(address & ~HPAGE_PMD_MASK);

	set_pmd_at(vma->vm_mm, address, pmdp, pmd);

	/* tlb flush only to serialize against gup-fast */

	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

	flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

}

#endif
@@ -179,7 +193,7 @@ void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, 
{

	pmd_t entry = *pmdp;

	set_pmd_at(vma->vm_mm, address, pmdp, pmd_mknotpresent(entry));

	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

	flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

}

#endif
@@ -196,7 +210,7 @@ pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address, 
	VM_BUG_ON(address & ~HPAGE_PMD_MASK);

	VM_BUG_ON(pmd_trans_huge(*pmdp));

	pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp);

	flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

	flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE);

	return pmd;

}

#endif