From: Will Deacon <will@kernel.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mike Rapoport <rppt@kernel.org>,
linux-mm@kvack.org, Russell King <linux@armlinux.org.uk>,
Catalin Marinas <catalin.marinas@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
David Hildenbrand <david@redhat.com>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC] mm: Enable generic pfn_valid() to handle early sections with memmap holes
Date: Thu, 11 Mar 2021 09:33:02 +0000 [thread overview]
Message-ID: <20210311093302.GA30603@willie-the-truck> (raw)
In-Reply-To: <003d8a4b-9687-3e9a-c27b-908db280b44c@arm.com>
On Thu, Mar 11, 2021 at 01:22:53PM +0530, Anshuman Khandual wrote:
> On 3/8/21 2:25 PM, Mike Rapoport wrote:
> > On Mon, Mar 08, 2021 at 08:57:53AM +0530, Anshuman Khandual wrote:
> >> Platforms like arm and arm64 have redefined pfn_valid() because their early
> >> memory sections might have contained memmap holes caused by memblock areas
> >> tagged with MEMBLOCK_NOMAP, which should be skipped while validating a pfn
> >> for struct page backing. This scenario could be captured with a new option
> >> CONFIG_HAVE_EARLY_SECTION_MEMMAP_HOLES and then generic pfn_valid() can be
> >> improved to accommodate such platforms. This reduces overall code footprint
> >> and also improves maintainability.
> >
> > I wonder whether arm64 would still need to free parts of its memmap after
>
> free_unused_memmap() is applicable when CONFIG_SPARSEMEM_VMEMMAP is not enabled.
> I am not sure whether there still might be some platforms or boards which would
> benefit from this. Hence lets just keep this unchanged for now.
In my opinion, unless there's a compelling reason for us to offer all of
these different implementations of the memmap on arm64 then we shouldn't
bother -- it's not like it's fun to maintain! Just use sparsemem vmemmap
and be done with it. Is there some reason we can't do that?
Will
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next prev parent reply other threads:[~2021-03-11 9:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-08 3:27 [RFC] mm: Enable generic pfn_valid() to handle early sections with memmap holes Anshuman Khandual
2021-03-08 8:37 ` David Hildenbrand
2021-03-11 4:29 ` Anshuman Khandual
2021-03-17 11:20 ` David Hildenbrand
2021-03-08 8:55 ` Mike Rapoport
2021-03-11 7:52 ` Anshuman Khandual
2021-03-11 8:14 ` Mike Rapoport
2021-03-11 9:33 ` Will Deacon [this message]
2021-03-11 10:43 ` Mike Rapoport
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