[PATCH v2 0/6] mm/mm_init.c: refactor free_area_init_core()

Baoquan He
2024-03-25T14:57:20Z

In function free_area_init_core(), the code calculating
zone->managed_pages and the subtracting dma_reserve from DMA zone looks
very confusing.

From git history, the code calculating zone->managed_pages was for
zone->present_pages originally. The early rough assignment is for
optimize zone's pcp and water mark setting. Later, managed_pages was
introduced into zone to represent the number of managed pages by buddy.
Now, zone->managed_pages is zeroed out and reset in mem_init() when
calling memblock_free_all(). zone's pcp and wmark setting relying on
actual zone->managed_pages are done later than mem_init() invocation.
So we don't need rush to early calculate and set zone->managed_pages,
just set it as zone->present_pages, will adjust it in mem_init().

And also add a new function calc_nr_kernel_pages() to count up free but
not reserved pages in memblock, then assign it to nr_all_pages and
nr_kernel_pages after memmap pages are allocated.

Changelog:
----------
v1->v2:
=======
These are all suggested by Mike, thanks to him.
- Swap the order of patch 1 and 2 in v1 to describe code change better,
Mike suggested this.
- Change to initializ zone->managed_pages as 0 in free_area_init_core()
as there isn't any page added into buddy system. And also improve the
ambiguous description in log. These are all in patch 4.

Baoquan He (6):
x86: remove unneeded memblock_find_dma_reserve()
mm/mm_init.c: remove the useless dma_reserve
mm/mm_init.c: add new function calc_nr_all_pages()
mm/mm_init.c: remove meaningless calculation of zone->managed_pages in
free_area_init_core()
mm/mm_init.c: remove unneeded calc_memmap_size()
mm/mm_init.c: remove arch_reserved_kernel_pages()

arch/powerpc/include/asm/mmu.h | 4 --
arch/powerpc/kernel/fadump.c | 5 --
arch/x86/include/asm/pgtable.h | 1 -
arch/x86/kernel/setup.c | 2 -
arch/x86/mm/init.c | 47 -------------
include/linux/mm.h | 4 --
mm/mm_init.c | 125 ++++++++-------------------------
7 files changed, 29 insertions(+), 159 deletions(-)

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2.41.0