Re: [PATCH] mm/hugetlb: reduce arch dependent code about huge_pmd_unshare

From: Steve Capper
Date: Fri Apr 24 2015 - 11:46:38 EST


On 23 April 2015 at 23:41, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Thu, 23 Apr 2015 22:26:18 +0000 "Luck, Tony" <tony.luck@xxxxxxxxx> wrote:
>> > Memory fails me. Why do some architectures (arm, arm64, x86_64) want
>> > huge_pmd_[un]share() while other architectures (ia64, tile, mips,
>> > powerpc, metag, sh, s390) do not?
>> Potentially laziness/ignorance-of-feature? It looks like this feature started on x86_64 and then spread
>> to arm*.
> Yes. In 3212b535f200c85b5a6 Steve Capper (ARM person) hoisted the code
> out of x86 into generic, then made arm use it.

I tested the pmd sharing code that x86 had and it worked well on ARM
too so I bundled it in when I generalised some of the huge page code.
I didn't know enough about the other architectures to enable it for
them, so played things safe by leaving it disabled for them.
Looking at this patch, I could have done that more cleanly though.

> We're not (I'm not) very good about letting arch people know about such
> things. I wonder how to fix that; does linux-arch work?

linux-arch is working for me, maybe a good idea to CC in some arch
maintainers too.

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