Re: [PATCH v9 0/6] optimize memblock_next_valid_pfn and early_pfn_valid on arm and arm64

On 7/2/2018 7:40 PM, Michal Hocko Wrote:

On Fri 29-06-18 10:29:17, Jia He wrote:

quoted

Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
where possible") tried to optimize the loop in memmap_init_zone(). But
there is still some room for improvement.

It would be great to shortly describe those optimization from high level
POV.

quoted

Patch 1 introduce new config to make codes more generic
Patch 2 remain the memblock_next_valid_pfn on arm and arm64
Patch 3 optimizes the memblock_next_valid_pfn()
Patch 4~6 optimizes the early_pfn_valid()

As for the performance improvement, after this set, I can see the time
overhead of memmap_init() is reduced from 27956us to 13537us in my
armv8a server(QDF2400 with 96G memory, pagesize 64k).

So this is 13ms saving when booting 96G machine. Is this really worth
the additional code? Are there any other benefits?

Sorry, Michal
I missed one thing.
This 13ms optimization is merely the result of my patch 3~6
Patch 1 is originated by Paul Burton in commit b92df1de5d289.
In its description,
===
James said "I have tested this patch on a virtual model of a Samurai CPU
    with a sparse memory map.  The kernel boot time drops from 109 to
    62 seconds. "
===

-- 
Cheers,
Jia

[...]

quoted

 arch/arm/Kconfig          |  4 +++
 arch/arm/mm/init.c        |  1 +
 arch/arm64/Kconfig        |  4 +++
 arch/arm64/mm/init.c      |  1 +
 include/linux/early_pfn.h | 79 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/memblock.h  |  2 ++
 include/linux/mmzone.h    | 18 ++++++++++-
 mm/Kconfig                |  3 ++
 mm/memblock.c             |  9 ++++++
 mm/page_alloc.c           |  5 ++-
 10 files changed, 124 insertions(+), 2 deletions(-)
 create mode 100644 include/linux/early_pfn.h