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 16:34:33 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     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 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?

Have you bisected the failure to the commit?

-- 
 Kirill A. Shutemov