linux-kernel - [PATCH 0/2] Optimize mmu_notifier->invalidate

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Date:   Mon, 16 Oct 2017 23:10:01 -0400
From:   jglisse@...hat.com
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org,
        Jérôme Glisse <jglisse@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        David Woodhouse <dwmw2@...radead.org>,
        Alistair Popple <alistair@...ple.id.au>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrew Donnellan <andrew.donnellan@....ibm.com>,
        iommu@...ts.linux-foundation.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH 0/2] Optimize mmu_notifier->invalidate_range callback

From: Jérôme Glisse <jglisse@...hat.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@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Joerg Roedel <jroedel@...e.de>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: Alistair Popple <alistair@...ple.id.au>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Stephen Rothwell <sfr@...b.auug.org.au>
Cc: Andrew Donnellan <andrew.donnellan@....ibm.com>
Cc: iommu@...ts.linux-foundation.org
Cc: linuxppc-dev@...ts.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