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Date:   Wed, 10 Oct 2018 17:50:39 -0700
From:   Joel Fernandes <>
To:     Joel Fernandes <>
Cc:     "Kirill A. Shutemov" <>,
        LKML <>,
        "open list:MEMORY MANAGEMENT" <>,
        "Cc: Android Kernel" <>,
        Minchan Kim <>,
        Hugh Dickins <>,
        Lokesh Gidra <>,
        Andrew Morton <>,
        Greg Kroah-Hartman <>,
        Kate Stewart <>,
        Philippe Ombredanne <>,
        Thomas Gleixner <>
Subject: Re: [PATCH] mm: Speed up mremap on large regions

On Wed, Oct 10, 2018 at 5:46 PM, Joel Fernandes <> wrote:
> On Wed, Oct 10, 2018 at 01:00:11PM +0300, Kirill A. Shutemov wrote:
>> My worry is that some architecture has to allocate page table differently
>> depending on virtual address (due to aliasing or something). Original page
>> table was allocated for one virtual address and moving the page table to
>> different spot in virtual address space may break the invariant.
>> > Also the clean up of the argument that you're proposing is a bit out of scope
>> > of this patch but yeah we could clean it up in a separate patch if needed. I
>> > don't feel too strongly about that. It seems cosmetic and in the future if
>> > the address that's passed in is needed, then the architecture can use it.
>> Please, do. This should be pretty mechanical change, but it will help to
>> make sure that none of obscure architecture will be broken by the change.
> The thing is its quite a lot of change, I wrote a coccinelle script to do it
> tree wide, following is the diffstat:
>  48 files changed, 91 insertions(+), 124 deletions(-)
> Imagine then having to add the address argument back in the future in case
> its ever needed. Is it really worth doing it? Anyway I confirmed that the
> address is NOT used for anything at the moment so your fears of the
> optimization doing anything wonky really don't exist at the moment. I really
> feel this is unnecessary but I am Ok with others agree the second arg to
> pte_alloc should be removed in light of this change. Andrew, what do you
> think?

I meant to say here, "I am Ok if others agree the second arg to
pte_alloc should be removed", but I would really like some input from
the others as well on what they think.

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