linux-kernel - Re: [tip:x86/mm] mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM

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Date:   Thu, 2 Nov 2017 13:42:42 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        kirill.shutemov@...ux.intel.com,
        Peter Zijlstra <peterz@...radead.org>, hpa@...or.com,
        Andrew Morton <akpm@...ux-foundation.org>, gorcunov@...nvz.org,
        luto@...capital.net, bp@...e.de,
        open list <linux-kernel@...r.kernel.org>,
        torvalds@...ux-foundation.org, Will Deacon <Will.Deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [tip:x86/mm] mm/sparsemem: Allocate mem_section at runtime for
 CONFIG_SPARSEMEM_EXTREME=y



On 02/11/17 13:34, Kirill A. Shutemov wrote:
> On Thu, Nov 02, 2017 at 12:31:54PM +0000, Sudeep Holla wrote:
>> (+Will, Catalin)
>>
>> On Fri, Oct 20, 2017 at 1:27 PM, tip-bot for Kirill A. Shutemov
>> <tipbot@...or.com> wrote:
>>> Commit-ID:  83e3c48729d9ebb7af5a31a504f3fd6aff0348c4
>>> Gitweb:     https://git.kernel.org/tip/83e3c48729d9ebb7af5a31a504f3fd6aff0348c4
>>> Author:     Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
>>> AuthorDate: Fri, 29 Sep 2017 17:08:16 +0300
>>> Committer:  Ingo Molnar <mingo@...nel.org>
>>> CommitDate: Fri, 20 Oct 2017 13:07:09 +0200
>>>
>>> mm/sparsemem: Allocate mem_section at runtime for CONFIG_SPARSEMEM_EXTREME=y
>>>
>>> Size of the mem_section[] array depends on the size of the physical address space.
>>>
>>> In preparation for boot-time switching between paging modes on x86-64
>>> we need to make the allocation of mem_section[] dynamic, because otherwise
>>> we waste a lot of RAM: with CONFIG_NODE_SHIFT=10, mem_section[] size is 32kB
>>> for 4-level paging and 2MB for 5-level paging mode.
>>>
>>> The patch allocates the array on the first call to sparse_memory_present_with_active_regions().
>>>
>>
>> I am seeing a boot failure with this patch in linux-next today(20171102)
> 
> Could you share the kernel config?
> 

It's the default config on arm64. Generated file is almost 160kB, I will
send it to you off-list.

> Have you bisected the failure to the commit?
> 
I just reverted this commit as I suspected that and it boots fine after
the revert.

-- 
Regards,
Sudeep