From: Matthew Wilcox <willy@infradead.org>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: mark.rutland@arm.com, christoffer.dall@arm.com,
linux-sh@vger.kernel.org, peterz@infradead.org,
catalin.marinas@arm.com, palmer@sifive.com, will.deacon@arm.com,
Michal Hocko <mhocko@kernel.org>,
linux-mm@kvack.org, linux-riscv@lists.infradead.org,
kvmarm@lists.cs.columbia.edu, aneesh.kumar@linux.ibm.com,
greentime@andestech.com, linux@armlinux.org.uk, mingo@redhat.com,
linux-arm-kernel@lists.infradead.org, rientjes@google.com,
dave.hansen@linux.intel.com,
Anshuman Khandual <anshuman.khandual@arm.com>,
marc.zyngier@arm.com, rppt@linux.vnet.ibm.com,
shakeelb@google.com, kirill@shutemov.name, tglx@linutronix.de,
vbabka@suse.cz, 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 V2] mm: Introduce GFP_PGTABLE
Date: Wed, 16 Jan 2019 06:20:14 -0800 [thread overview]
Message-ID: <20190116142014.GJ6310@bombadil.infradead.org> (raw)
In-Reply-To: <521d8511-4c87-49c6-de03-67a71d5bacca@c-s.fr>
On Wed, Jan 16, 2019 at 02:47:16PM +0100, Christophe Leroy wrote:
> Le 16/01/2019 à 14:18, Matthew Wilcox a écrit :
> > I disagree with your objective. Making more code common is a great idea,
> > but this patch is too unambitious. We should be heading towards one or
> > two page table allocation functions instead of having every architecture do
> > its own thing.
> >
> > So start there. Move the x86 function into common code and convert one
> > other architecture to use it too.
>
> Are we talking about pte_alloc_one_kernel() and pte_alloc_one() ?
>
> I'm not sure x86 function is the best common one, as it seems to allocate a
> multiple of PAGE_SIZE only.
And that's the common case. Most architectures use a single page for at
least one level of the pte/pmd/pud/p4d/pgd hierarchy. Some use multiple
pages and some use a fraction of a page.
> Some arches like powerpc use pagetables which are smaller than a page, for
> instance powerpc 8xx uses 4k pagetables even with 16k pages, which means a
> single page can be used by 4 pagetables.
Those can be added later. Note I said "one or two", and that's what I
had in mind; I think we want one function that allocates just a page
and another that allocates a page fragment. Then we can have a good
discussion about what method we use; s390 and ppc use different techniques
today and there's really no good reason for that.
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next prev parent reply other threads:[~2019-01-16 14:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-16 6:21 [PATCH V2] mm: Introduce GFP_PGTABLE Anshuman Khandual
2019-01-16 6:55 ` Mike Rapoport
2019-01-16 12:53 ` Anshuman Khandual
2019-01-16 6:57 ` Michal Hocko
2019-01-16 12:30 ` Matthew Wilcox
2019-01-16 12:34 ` Peter Zijlstra
2019-01-16 12:44 ` Michal Hocko
2019-01-16 13:27 ` Anshuman Khandual
2019-01-16 13:36 ` Michal Hocko
2019-01-16 13:12 ` Anshuman Khandual
2019-01-16 13:18 ` Matthew Wilcox
2019-01-16 13:33 ` Michal Hocko
2019-01-16 13:47 ` Christophe Leroy
2019-01-16 14:20 ` Matthew Wilcox [this message]
2019-01-17 9:56 ` Michael Ellerman
2019-01-16 7:10 ` Christophe Leroy
2019-01-16 12:39 ` Anshuman Khandual
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