On 7/2/2018 7:40 PM, Michal Hocko Wrote:
> On Fri 29-06-18 10:29:17, Jia He wrote:
>> 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.
>
>>
>> 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
> [...]
>> 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
>
