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From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Matthew Wilcox <willy@infradead.org>,
	Christophe Leroy <christophe.leroy@c-s.fr>
Cc: mark.rutland@arm.com, mhocko@suse.com, linux-sh@vger.kernel.org,
	peterz@infradead.org, catalin.marinas@arm.com,
	dave.hansen@linux.intel.com, will.deacon@arm.com,
	christoffer.dall@arm.com, linux-mm@kvack.org,
	kvmarm@lists.cs.columbia.edu, aneesh.kumar@linux.ibm.com,
	linux@armlinux.org.uk, mingo@redhat.com, vbabka@suse.cz,
	rientjes@google.com, marc.zyngier@arm.com,
	rppt@linux.vnet.ibm.com, shakeelb@google.com,
	kirill@shutemov.name, tglx@linutronix.de,
	linux-arm-kernel@lists.infradead.org, ard.biesheuvel@linaro.org,
	linuxppc-dev@lists.ozlabs.org, steve.capper@arm.com,
	linux-kernel@vger.kernel.org, james.morse@arm.com,
	akpm@linux-foundation.org, robin.murphy@arm.com
Subject: Re: [PATCH] mm: Introduce GFP_PGTABLE
Date: Mon, 14 Jan 2019 09:58:14 +0530
Message-ID: <48f81a76-2b2d-5060-d9bc-c42d5b5975c3@arm.com> (raw)
In-Reply-To: <20190112154944.GT6310@bombadil.infradead.org>



On 01/12/2019 09:19 PM, Matthew Wilcox wrote:
> On Sat, Jan 12, 2019 at 02:49:29PM +0100, Christophe Leroy wrote:
>> As far as I can see,
>>
>> #define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT)
>>
>> So what's the difference between:
>>
>> (GFP_KERNEL_ACCOUNT | __GFP_ZERO) & ~__GFP_ACCOUNT
>>
>> and
>>
>> (GFP_KERNEL | __GFP_ZERO) & ~__GFP_ACCOUNT
> 
> Nothing.  But there's a huge difference in the other parts of that same
> file where GFP_ACCOUNT is _not_ used.
> 
> I think this unification is too small to bother with.  Something I've
> had on my todo list for some time and have not done anything about
> is to actually unify all of the architecture pte/pmd/... allocations.
> There are tricks some architectures use that others would benefit from.

Sure. Could you please elaborate on this ?

Invariably all kernel pgtable page allocations should use GFP_PGTABLE and
all user page table allocation should use (GFP_PGTABLE | __GFP_ACCOUNT).
Ideally there should be default generic functions user_pgtable_gfp() or
kernel_pgtable_gfp() returning these values. Overrides can be provided if
an arch still wants some more control.


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Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-12 10:26 Anshuman Khandual
2019-01-12 12:12 ` Matthew Wilcox
2019-01-12 12:55   ` Anshuman Khandual
2019-01-12 13:49   ` Christophe Leroy
2019-01-12 15:49     ` Matthew Wilcox
2019-01-12 16:50       ` Shakeel Butt
2019-01-14  4:28       ` Anshuman Khandual [this message]
2019-01-12 16:48 ` Shakeel Butt
2019-01-14  4:14   ` Anshuman Khandual
2019-01-13 17:35 ` Michal Hocko
2019-01-14  4:00   ` Anshuman Khandual
2019-01-14  7:01     ` Michal Hocko
2019-01-15 14:11       ` Anshuman Khandual

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