linux-kernel - Re: [PATCH v2 6/6] RISC-V: Implement sparsemem

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Message-ID: <5fd0880c-5896-ffee-4d3c-4fce1649382e@deltatee.com>
Date:   Mon, 17 Dec 2018 09:50:30 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Nick Kossifidis <mick@....forth.gr>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-sh@...r.kernel.org,
        Rob Herring <robh@...nel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Waterman <andrew@...ive.com>,
        Arnd Bergmann <arnd@...db.de>,
        Palmer Dabbelt <palmer@...ive.com>,
        Stephen Bates <sbates@...thlin.com>,
        Zong Li <zong@...estech.com>, Olof Johansson <olof@...om.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michael Clark <michaeljclark@....com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2 6/6] RISC-V: Implement sparsemem



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