From: Hubert Ralf <Ralf.Hubert@preh.de>
To: "james.morse@arm.com" <james.morse@arm.com>
Cc: "linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] aarch64/mm: speedup memory initialisation
Date: Thu, 12 Sep 2019 05:36:53 +0000 [thread overview]
Message-ID: <92d07b70571fd76a7502faa6d199d4d11c498b20.camel@preh.de> (raw)
In-Reply-To: <93e5d420-91b7-0e42-7d3f-776323abe450@arm.com>
Hi James,
On 09/11/2019, 17:22 +0100 James Morse wrote:
> Hi Hubert,
>
> (Subject-Nit: The prefix for this part of the kernel is 'arm64: mm:'.
> git log --oneline $file will usually give you enough examples you can
> spot the pattern.)
Thanks for the hint.
>
> On 9/10/19 9:59 AM, Hubert Ralf wrote:
> > On ARM64 memmap_init_zone is used during bootmem_init, which iterates over
> > all pages in the memory starting at the lowest address until the highest
> > address is reached. On arm64 this ends up in searching a memmory region
> > containing for each single page between lowest and highest available
> > physicall address.
> > Having a sparse memory system there may be some big holes in the
> > memory map. For each page in this holes a lookup is done, which is
> > implemented as a binary search on the available memory blocks.
> >
> > Adding a memmap_init for aarch64 to do the init only for the available
> > memory areas reduces the time needed for initialising memory on startup.
> > On a Renesas R-CAR M3 based system with a total hole of 20GB bootmem_init
> > execution time is reduced from 378ms to 84ms.
>
> Hmm, there is nothing arm64 specific about this SPARSEMEM behaviour.
> Is there any reason this can't be done in core code, where it would
> benefit other architectures too?
I'll try to move this to the core code.
>
> (You'd need it to depend on !ARCH_DISCARD_MEMBLOCK as it looks like
> memory-hotplug uses this late).
>
>
> Thanks,
>
> James
Thanks,
Ralf
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next prev parent reply other threads:[~2019-09-12 5:37 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-10 8:59 [PATCH] aarch64/mm: speedup memory initialisation Hubert Ralf
2019-09-10 13:07 ` Robin Murphy
2019-09-11 16:22 ` James Morse
2019-09-12 5:36 ` Hubert Ralf [this message]
2019-09-12 8:12 ` Anshuman Khandual
2019-09-12 8:40 ` Hubert Ralf
2019-09-12 8:59 ` Anshuman Khandual
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