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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>, Rashmica Gupta <rashmicy@gmail.com>,
 linuxppc-dev@lists.ozlabs.org
Subject: Re: [V2] powerpc/Kconfig: Update config option based on page size.
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Date: Tue, 19 Apr 2016 10:59:29 -0400
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Michael Ellerman <mpe@ellerman.id.au> writes:

> On Fri, 2016-19-02 at 05:38:47 UTC, Rashmica Gupta wrote:
>> Currently on PPC64 changing kernel pagesize from 4K to 64K leaves
>> FORCE_MAX_ZONEORDER set to 13 - which produces a compile error.
>> 
> ...
>> So, update the range of FORCE_MAX_ZONEORDER from 9-64 to 8-9 for 64K pages
>> and from 13-64 to 9-13 for 4K pages.
>> 
>> Signed-off-by: Rashmica Gupta <rashmicy@gmail.com>
>> Reviewed-by: Balbir Singh <bsingharora@gmail.com>
>
> Applied to powerpc next, thanks.
>
> https://git.kernel.org/powerpc/c/a7ee539584acf4a565b7439cea
>

HPAGE_PMD_ORDER is not something we should check w.r.t 4k linux page
size. We do have the below constraint w.r.t hugetlb pages

static inline bool hstate_is_gigantic(struct hstate *h)
{
	return huge_page_order(h) >= MAX_ORDER;
}

That require MAX_ORDER to be greater than 12.

Did we test hugetlbfs 4k config with this patch ? Will it work if we
start marking hugepage as gigantic page ?

-aneesh