linux-kernel - [PATCH v2 0/6] mm/mm_init.c: refactor free_area_init

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Date: Mon, 25 Mar 2024 22:56:40 +0800
From: Baoquan He <bhe@...hat.com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
	x86@...nel.org,
	linuxppc-dev@...ts.ozlabs.org,
	akpm@...ux-foundation.org,
	rppt@...nel.org,
	Baoquan He <bhe@...hat.com>
Subject: [PATCH v2 0/6] mm/mm_init.c: refactor free_area_init_core()

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(-)

-- 
2.41.0