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mm,thp: introduce flush_pmd_tlb_range

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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: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: http://lkml.kernel.org/r/20151009100816.GC7873@node
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2015-02-20 10:36:28 +05:30
parent bd5e88ad72
commit 12ebc1581a
2 changed files with 21 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
mm/huge_memory.c
View File

@ -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

26
mm/pgtable-generic.c
View File

@ -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