[PATCH 0/2] Optimize mmu_notifier->invalidate_range callback

[jglisse at redhat.com]

From: Jérôme Glisse <jglisse at redhat.com>

(Andrew you already have v1 in your queue of patch 1, patch 2 is new,
 i think you can drop it patch 1 v1 for v2, v2 is bit more conservative
 and i fixed typos)

All this only affect user of invalidate_range callback (at this time
CAPI arch/powerpc/platforms/powernv/npu-dma.c, IOMMU ATS/PASID in
drivers/iommu/amd_iommu_v2.c|intel-svm.c)

This patchset remove useless double call to mmu_notifier->invalidate_range
callback wherever it is safe to do so. The first patch just remove useless
call and add documentation explaining why it is safe to do so. The second
patch go further by introducing mmu_notifier_invalidate_range_only_end()
which skip callback to invalidate_range this can be done when clearing a
pte, pmd or pud with notification which call invalidate_range right after
clearing under the page table lock.

It should improve performances but i am lacking hardware and benchmarks
which might show an improvement. Maybe folks in cc can help here.

Cc: Andrea Arcangeli <aarcange at redhat.com>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Joerg Roedel <jroedel at suse.de>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit at amd.com>
Cc: David Woodhouse <dwmw2 at infradead.org>
Cc: Alistair Popple <alistair at popple.id.au>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Stephen Rothwell <sfr at canb.auug.org.au>
Cc: Andrew Donnellan <andrew.donnellan at au1.ibm.com>
Cc: iommu at lists.linux-foundation.org
Cc: linuxppc-dev at lists.ozlabs.org

Jérôme Glisse (2):
  mm/mmu_notifier: avoid double notification when it is useless v2
  mm/mmu_notifier: avoid call to invalidate_range() in range_end()

 Documentation/vm/mmu_notifier.txt | 93 +++++++++++++++++++++++++++++++++++++++
 fs/dax.c                          |  9 +++-
 include/linux/mmu_notifier.h      | 20 +++++++--
 mm/huge_memory.c                  | 66 ++++++++++++++++++++++++---
 mm/hugetlb.c                      | 16 +++++--
 mm/ksm.c                          | 15 ++++++-
 mm/memory.c                       |  6 ++-
 mm/migrate.c                      | 15 +++++--
 mm/mmu_notifier.c                 | 11 ++++-
 mm/rmap.c                         | 59 ++++++++++++++++++++++---
 10 files changed, 281 insertions(+), 29 deletions(-)
 create mode 100644 Documentation/vm/mmu_notifier.txt

-- 
2.13.6