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?
[...]
> 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
--
Michal Hocko
SUSE Labs
