Re: [PATCH v2 0/3] mm/sparse: Optimize memmap allocation during sparse_init()

From: Baoquan He
Date: Thu Feb 22 2018 - 04:15:56 EST


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
>