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

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Date:   Thu, 19 Oct 2017 13:43:19 +1100
From:   Balbir Singh <bsingharora@...il.com>
To:     jglisse@...hat.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        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: Re: [PATCH 0/2] Optimize mmu_notifier->invalidate_range callback

On Mon, 16 Oct 2017 23:10:01 -0400
jglisse@...hat.com wrote:

> 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

As in an extra call? Where does that come from?

> 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.
>

Balbir Singh.