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From: Logan Gunthorpe <logang@deltatee.com>
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Date: Mon, 17 Dec 2018 09:50:30 -0700
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Subject: Re: [PATCH v2 6/6] RISC-V: Implement sparsemem
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To: Nick Kossifidis <mick@ics.forth.gr>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-sh@vger.kernel.org, Rob Herring <robh@kernel.org>, Albert Ou <aou@eecs.berkeley.edu>, Andrew Waterman <andrew@sifive.com>, Arnd Bergmann <arnd@arndb.de>, Palmer Dabbelt <palmer@sifive.com>, Stephen Bates <sbates@raithlin.com>, Zong Li <zong@andestech.com>, Olof Johansson <olof@lixom.net>, Andrew Morton <akpm@linux-foundation.org>, Michael Clark <michaeljclark@mac.com>, Christoph Hellwig <hch@lst.de>



On 2018-12-17 7:59 a.m., Nick Kossifidis wrote:
> Having memory blocks of a minimum size of 1GB doesn't make much sense. 
> It makes it harder to implement hotplug on top of this since we'll only 
> able to add/remove 1GB at a time. ARM used to do the same and they 
> switched to 27bits (https://patchwork.kernel.org/patch/9172845/), ARM64 
> still uses 1GB, x86 also uses 27bits and most archs also use something 
> below 30. I believe we should go for 27bits as well or even better have 
> this as a compile time option.

Thanks, that makes sense. I'll make the change for the next time we submit.

> BTW memblocks_present is on master now (got merged 3 days ago).

Great! We'll send an updated patch set after the merge window.

Logan