linux-kernel - Re: [RFC 4/9] powerpc/mm: Split huge_pte

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Date:	Thu, 10 Mar 2016 11:03:44 +0530
From:	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
CC:	hughd@...gle.com, kirill@...temov.name, n-horiguchi@...jp.nec.com,
	mgorman@...hsingularity.net, akpm@...ux-foundation.org
Subject: Re: [RFC 4/9] powerpc/mm: Split huge_pte_alloc function for BOOK3S
 64K

On 03/10/2016 01:25 AM, Aneesh Kumar K.V wrote:
> Anshuman Khandual <khandual@...ux.vnet.ibm.com> writes:
> 
>> > [ text/plain ]
>> > From: root <root@...alpine2-lp8.aus.stglabs.ibm.com>
>> >
>> > Currently the 'huge_pte_alloc' function has two versions, one for the
>> > BOOK3S and the other one for the BOOK3E platforms. This change splits
>> > the BOOK3S version into two parts, one for the 4K page size based
>> > implementation and the other one for the 64K page sized implementation.
>> > This change is one of the prerequisites towards enabling GENERAL_HUGETLB
>> > implementation for BOOK3S 64K based huge pages.
> I really wish we reduce #ifdefs in C code and start splitting hash
> and nonhash code out where ever we can.

Okay but here we are only dealing with 64K and 4K configs inside book3s.
I guess it covers both hash and no hash implementations. Not sure if I
got it correctly.

> 
> What we really want here is a book3s version and in book3s version use
> powerpc specific huge_pte_alloc only if GENERAL_HUGETLB was not defined.

got it.

> Don't limit it to 64k linux page size. We should select between powerpc
> specific implementation and generic code using GENERAL_HUGETLB define.

Got it. will try.