From: Matthew Wilcox <willy@infradead.org>
To: Yu Zhao <yuzhao@google.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
"Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Nick Piggin <npiggin@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Joel Fernandes <joel@joelfernandes.org>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Mark Rutland <mark.rutland@arm.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Chintan Pandya <cpandya@codeaurora.org>,
Jun Yao <yaojun8558363@gmail.com>,
Laura Abbott <labbott@redhat.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v2 1/3] arm64: mm: use appropriate ctors for page tables
Date: Wed, 20 Feb 2019 12:59:30 -0800 [thread overview]
Message-ID: <20190220205930.GL12668@bombadil.infradead.org> (raw)
In-Reply-To: <20190220202244.GA80497@google.com>
On Wed, Feb 20, 2019 at 01:22:44PM -0700, Yu Zhao wrote:
> On Wed, Feb 20, 2019 at 03:57:59PM +0530, Anshuman Khandual wrote:
> > Using pgtable_pmd_page_ctor() during PMD level pgtable page allocation
> > as suggested in the patch breaks pmd_alloc_one() changes as per the
> > previous proposal. Hence we all would need some agreement here.
> >
> > https://www.spinics.net/lists/arm-kernel/msg701960.html
>
> A proposal that requires all page tables to go through a same set of
> ctors on all archs is not only inefficient (for kernel page tables)
> but also infeasible (for arches use kmem for page tables). I've
> explained this clearly.
>
> The generalized page table functions must recognize the differences
> on different levels and between user and kernel page tables, and
> provide unified api that is capable of handling the differences.
The two architectures I'm aware of (s390 and power) which use sub-page
allocations for page tables do so by allocating entire pages and then
implementing their own allocators. It shouldn't be a huge problem to
use a ctor for the pages. We can probably even implement a dtor for them.
Oh, another corner-case I've just remembered is x86-32's PAE with four
8-byte entries in the PGD. That should also go away and be replaced
with a shared implementation of sub-page allocations which can also be
marked as PageTable.
Ideally PTEs, PMDs, etc, etc would all be accounted to the individual
processes causing them to be allocated. This isn't really feasible
with the x86 PGD; by definition there's only one per process. I'm OK
with failing to account this 32-byte allocation to the task though.
So maybe the pgd_cache can remain separate from the hypothetical unified
ppc/s390 code.
next prev parent reply other threads:[~2019-02-20 20:59 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-14 21:16 [PATCH] arm64: mm: enable per pmd page table lock Yu Zhao
2019-02-18 15:12 ` Will Deacon
2019-02-18 19:49 ` Yu Zhao
2019-02-18 20:48 ` Yu Zhao
2019-02-19 4:09 ` Anshuman Khandual
2019-02-18 23:13 ` [PATCH v2 1/3] arm64: mm: use appropriate ctors for page tables Yu Zhao
2019-02-18 23:13 ` [PATCH v2 2/3] arm64: mm: don't call page table ctors for init_mm Yu Zhao
2019-02-26 15:13 ` Mark Rutland
2019-03-09 3:52 ` Yu Zhao
2019-02-18 23:13 ` [PATCH v2 3/3] arm64: mm: enable per pmd page table lock Yu Zhao
2019-02-19 4:21 ` [PATCH v2 1/3] arm64: mm: use appropriate ctors for page tables Anshuman Khandual
2019-02-19 5:32 ` Yu Zhao
2019-02-19 6:17 ` Anshuman Khandual
2019-02-19 22:28 ` Yu Zhao
2019-02-20 10:27 ` Anshuman Khandual
2019-02-20 12:24 ` Matthew Wilcox
2019-02-20 20:22 ` Yu Zhao
2019-02-20 20:59 ` Matthew Wilcox [this message]
2019-02-20 1:34 ` Matthew Wilcox
2019-02-20 3:20 ` Anshuman Khandual
2019-02-20 21:03 ` Matthew Wilcox
2019-02-26 15:12 ` Mark Rutland
2019-03-09 4:01 ` Yu Zhao
2019-03-10 1:19 ` [PATCH v3 " Yu Zhao
2019-03-10 1:19 ` [PATCH v3 2/3] arm64: mm: don't call page table ctors for init_mm Yu Zhao
2019-03-10 1:19 ` [PATCH v3 3/3] arm64: mm: enable per pmd page table lock Yu Zhao
2019-03-11 8:28 ` Anshuman Khandual
2019-03-11 23:10 ` Yu Zhao
2019-03-11 12:12 ` Mark Rutland
2019-03-11 12:57 ` Anshuman Khandual
2019-03-11 23:11 ` Yu Zhao
2019-03-11 7:45 ` [PATCH v3 1/3] arm64: mm: use appropriate ctors for page tables Anshuman Khandual
2019-03-11 23:23 ` Yu Zhao
2019-03-12 0:57 ` [PATCH v4 1/4] " Yu Zhao
2019-03-12 0:57 ` [PATCH v4 2/4] arm64: mm: don't call page table ctors for init_mm Yu Zhao
2019-03-12 0:57 ` [PATCH v4 3/4] arm64: mm: call ctor for stage2 pmd page Yu Zhao
2019-03-12 2:19 ` [PATCH] KVM: ARM: Remove pgtable page standard functions from stage-2 page tables Anshuman Khandual
2019-03-12 2:40 ` Yu Zhao
2019-03-12 10:37 ` Suzuki K Poulose
2019-03-12 11:31 ` Anshuman Khandual
2019-03-12 11:43 ` Suzuki K Poulose
2019-03-12 13:25 ` [PATCH V2] " Anshuman Khandual
2019-04-01 16:16 ` Will Deacon
2019-04-01 18:34 ` Yu Zhao
2019-04-02 9:03 ` Will Deacon
2019-04-08 14:22 ` Will Deacon
2019-04-08 17:18 ` Yu Zhao
2019-04-08 9:09 ` Marc Zyngier
2019-03-12 0:57 ` [PATCH v4 4/4] arm64: mm: enable per pmd page table lock Yu Zhao
2019-02-19 3:08 ` [PATCH] " Anshuman Khandual
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