From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: mark.rutland@arm.com, linux-sh@vger.kernel.org,
peterz@infradead.org, catalin.marinas@arm.com,
dave.hansen@linux.intel.com, will.deacon@arm.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
kvmarm@lists.cs.columbia.edu, mpe@ellerman.id.au,
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,
robin.murphy@arm.com, steve.capper@arm.com,
christoffer.dall@arm.com, james.morse@arm.com,
aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] mm: Introduce GFP_PGTABLE
Date: Mon, 14 Jan 2019 09:30:55 +0530 [thread overview]
Message-ID: <f9f333a5-5533-996a-dc8e-1ff1096c1d19@arm.com> (raw)
In-Reply-To: <20190113173555.GC1578@dhcp22.suse.cz>
On 01/13/2019 11:05 PM, Michal Hocko wrote:
> On Sat 12-01-19 15:56:38, Anshuman Khandual wrote:
>> All architectures have been defining their own PGALLOC_GFP as (GFP_KERNEL |
>> __GFP_ZERO) and using it for allocating page table pages. This causes some
>> code duplication which can be easily avoided. GFP_KERNEL allocated and
>> cleared out pages (__GFP_ZERO) are required for page tables on any given
>> architecture. This creates a new generic GFP flag flag which can be used
>> for any page table page allocation. Does not cause any functional change.
>
> I agree that some unification is due but GFP_PGTABLE is not something to
> expose in generic gfp.h IMHO. It just risks an abuse. I would be looking
Why would you think that it risks an abuse ? It does not create new semantics
of allocation in the buddy. Its just uses existing GFP_KERNEL allocation which
is then getting zeroed out. The risks (if any) is exactly same as GFP_KERNEL.
> at providing asm-generic implementation and reuse it to remove the code
Does that mean GFP_PGTABLE can be created but not in gfp.h but in some other
memory related header file ?
> duplication. But I haven't tried that to know that it will work out due
> to small/subtle differences between arches.
IIUC from the allocation perspective GFP_ACCOUNT is the only thing which gets
added with GFP_PGTABLE for user page table for memcg accounting purpose. There
does not seem to be any other differences unless I am missing something.
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next prev parent reply other threads:[~2019-01-14 4:01 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-12 10:26 [PATCH] mm: Introduce GFP_PGTABLE 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
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 [this message]
2019-01-14 7:01 ` Michal Hocko
2019-01-15 14:11 ` Anshuman Khandual
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