Subject: + mm-use-paravirt-friendly-ops-for-numa-hinting-ptes.patch added to
-mm tree
To:
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From: [email protected]
Date: Tue, 15 Apr 2014 13:17:30 -0700
The patch titled
Subject: mm: use paravirt friendly ops for NUMA hinting ptes
has been added to the -mm tree. Its filename is
mm-use-paravirt-friendly-ops-for-numa-hinting-ptes.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-use-paravirt-friendly-ops-for-numa-hinting-ptes.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-use-paravirt-friendly-ops-for-numa-hinting-ptes.patch
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------------------------------------------------------
From: Mel Gorman <[email protected]>
Subject: mm: use paravirt friendly ops for NUMA hinting ptes
David Vrabel identified a regression when using automatic NUMA balancing
under Xen whereby page table entries were getting corrupted due to the use
of native PTE operations. Quoting him
Xen PV guest page tables require that their entries use machine
addresses if the preset bit (_PAGE_PRESENT) is set, and (for
successful migration) non-present PTEs must use pseudo-physical
addresses. This is because on migration MFNs in present PTEs are
translated to PFNs (canonicalised) so they may be translated back
to the new MFN in the destination domain (uncanonicalised).
pte_mknonnuma(), pmd_mknonnuma(), pte_mknuma() and pmd_mknuma()
set and clear the _PAGE_PRESENT bit using pte_set_flags(),
pte_clear_flags(), etc.
In a Xen PV guest, these functions must translate MFNs to PFNs
when clearing _PAGE_PRESENT and translate PFNs to MFNs when setting
_PAGE_PRESENT.
His suggested fix converted p[te|md]_[set|clear]_flags to using
paravirt-friendly ops but this is overkill. He suggested an alternative
of using p[te|md]_modify in the NUMA page table operations but this is
does more work than necessary and would require looking up a VMA for
protections.
This patch modifies the NUMA page table operations to use paravirt
friendly operations to set/clear the flags of interest. Unfortunately
this will take a performance hit when updating the PTEs on CONFIG_PARAVIRT
but I do not see a way around it that does not break Xen.
Signed-off-by: Mel Gorman <[email protected]>
Acked-by: David Vrabel <[email protected]>
Tested-by: David Vrabel <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Anvin <[email protected]>
Cc: Fengguang Wu <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Steven Noonan <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Srikar Dronamraju <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
include/asm-generic/pgtable.h | 31 +++++++++++++++++++++++--------
1 file changed, 23 insertions(+), 8 deletions(-)
diff -puN
include/asm-generic/pgtable.h~mm-use-paravirt-friendly-ops-for-numa-hinting-ptes
include/asm-generic/pgtable.h
---
a/include/asm-generic/pgtable.h~mm-use-paravirt-friendly-ops-for-numa-hinting-ptes
+++ a/include/asm-generic/pgtable.h
@@ -693,24 +693,35 @@ static inline int pmd_numa(pmd_t pmd)
#ifndef pte_mknonnuma
static inline pte_t pte_mknonnuma(pte_t pte)
{
- pte = pte_clear_flags(pte, _PAGE_NUMA);
- return pte_set_flags(pte, _PAGE_PRESENT|_PAGE_ACCESSED);
+ pteval_t val = pte_val(pte);
+
+ val &= ~_PAGE_NUMA;
+ val |= (_PAGE_PRESENT|_PAGE_ACCESSED);
+ return __pte(val);
}
#endif
#ifndef pmd_mknonnuma
static inline pmd_t pmd_mknonnuma(pmd_t pmd)
{
- pmd = pmd_clear_flags(pmd, _PAGE_NUMA);
- return pmd_set_flags(pmd, _PAGE_PRESENT|_PAGE_ACCESSED);
+ pmdval_t val = pmd_val(pmd);
+
+ val &= ~_PAGE_NUMA;
+ val |= (_PAGE_PRESENT|_PAGE_ACCESSED);
+
+ return __pmd(val);
}
#endif
#ifndef pte_mknuma
static inline pte_t pte_mknuma(pte_t pte)
{
- pte = pte_set_flags(pte, _PAGE_NUMA);
- return pte_clear_flags(pte, _PAGE_PRESENT);
+ pteval_t val = pte_val(pte);
+
+ val &= ~_PAGE_PRESENT;
+ val |= _PAGE_NUMA;
+
+ return __pte(val);
}
#endif
@@ -729,8 +740,12 @@ static inline void ptep_set_numa(struct
#ifndef pmd_mknuma
static inline pmd_t pmd_mknuma(pmd_t pmd)
{
- pmd = pmd_set_flags(pmd, _PAGE_NUMA);
- return pmd_clear_flags(pmd, _PAGE_PRESENT);
+ pmdval_t val = pmd_val(pmd);
+
+ val &= ~_PAGE_PRESENT;
+ val |= _PAGE_NUMA;
+
+ return __pmd(val);
}
#endif
_
Patches currently in -mm which might be from [email protected] are
mm-use-paravirt-friendly-ops-for-numa-hinting-ptes.patch
x86-require-x86-64-for-automatic-numa-balancing.patch
x86-define-_page_numa-by-reusing-software-bits-on-the-pmd-and-pte-levels.patch
mm-introduce-do_shared_fault-and-drop-do_fault-fix-fix.patch
mm-compactionc-isolate_freepages_block-small-tuneup.patch
mm-only-force-scan-in-reclaim-when-none-of-the-lrus-are-big-enough.patch
do_shared_fault-check-that-mmap_sem-is-held.patch
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