linux-kernel - Re: [PATCH v2 0/3] mm/sparse: Optimize memmap allocation during sparse

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Date:   Thu, 22 Feb 2018 17:15:46 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org, dave.hansen@...el.com
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        kirill.shutemov@...ux.intel.com, mhocko@...e.com,
        tglx@...utronix.de
Subject: Re: [PATCH v2 0/3] mm/sparse: Optimize memmap allocation during
 sparse_init()

On 02/22/18 at 05:11pm, Baoquan He wrote:
> This is v2 post. V1 can be found here:
> https://www.spinics.net/lists/linux-mm/msg144486.html
> 
> In sparse_init(), two temporary pointer arrays, usemap_map and map_map
> are allocated with the size of NR_MEM_SECTIONS. They are used to store
> each memory section's usemap and mem map if marked as present. In
> 5-level paging mode, this will cost 512M memory though they will be
> released at the end of sparse_init(). System with few memory, like
> kdump kernel which usually only has about 256M, will fail to boot
> because of allocation failure if CONFIG_X86_5LEVEL=y.
> 
> In this patchset, optimize the memmap allocation code to only use
> usemap_map and map_map with the size of nr_present_sections. This
> makes kdump kernel boot up with normal crashkernel='' setting when
> CONFIG_X86_5LEVEL=y.

Sorry, forgot adding the change log.

v1-v2:
  Split out the nr_present_sections adding as a single patch for easier
  reviewing.

  Rewrite patch log according to Dave's suggestion.

  Fix code bug in patch 0002 reported by test robot.

> 
> Baoquan He (3):
>   mm/sparse: Add a static variable nr_present_sections
>   mm/sparsemem: Defer the ms->section_mem_map clearing
>   mm/sparse: Optimize memmap allocation during sparse_init()
> 
>  mm/sparse-vmemmap.c |  9 +++++----
>  mm/sparse.c         | 54 +++++++++++++++++++++++++++++++++++------------------
>  2 files changed, 41 insertions(+), 22 deletions(-)
> 
> -- 
> 2.13.6
>