On Wed, Sep 25, 2024 at 07:02:35PM +0800, suhua wrote:
> After sparse_init function requests memory for struct page in memblock and
> adds it to memblock.reserved, this memory area is present in both
> memblock.memory and memblock.reserved.
>
> When CONFIG_DEFERRED_STRUCT_PAGE_INIT is not set. The memmap_init function
> is called during the initialization of the free area of the zone, this
> function calls for_each_mem_pfn_range to initialize all memblock.memory,
> excluding memory that is also placed in memblock.reserved, such as the
> struct page metadata that describes the page, 1TB memory is about 16GB,
> and generally this part of reserved memory occupies more than 90% of the
> total reserved memory of the system. So all memory in memblock.memory is
> set to MIGRATE_MOVABLE according to the alignment of pageblock_nr_pages.
> For example, if hugetlb_optimize_vmemmap=1, huge pages are allocated, the
> freed pages are placed on buddy's MIGRATE_MOVABL list for use.
Please make sure you spell MIGRATE_MOVABLE and MIGRATE_UNMOVABLE correctly.
> When CONFIG_DEFERRED_STRUCT_PAGE_INIT=y, only the first_deferred_pfn range
> is initialized in memmap_init. The subsequent free_low_memory_core_early
> initializes all memblock.reserved memory but not MIGRATE_MOVABL. All
> memblock.memory is set to MIGRATE_MOVABL when it is placed in buddy via
> free_low_memory_core_early and deferred_init_memmap. As a result, when
> hugetlb_optimize_vmemmap=1 and huge pages are allocated, the freed pages
> will be placed on buddy's MIGRATE_UNMOVABL list (For example, on machines
> with 1TB of memory, alloc 2MB huge page size of 1000GB frees up about 15GB
> to MIGRATE_UNMOVABL). Since the huge page alloc requires a MIGRATE_MOVABL
> page, a fallback is performed to alloc memory from MIGRATE_UNMOVABL for
> MIGRATE_MOVABL.
>
> Large amount of UNMOVABL memory is not conducive to defragmentation, so
> the reserved memory is also set to MIGRATE_MOVABLE in the
> free_low_memory_core_early phase following the alignment of
> pageblock_nr_pages.
>
> Eg：
> echo 500000 > /proc/sys/vm/nr_hugepages
> cat /proc/pagetypeinfo
>
> before：
> Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
> …
> Node 0, zone Normal, type Unmovable 51 2 1 28 53 35 35 43 40 69 3852
> Node 0, zone Normal, type Movable 6485 4610 666 202 200 185 208 87 54 2 240
> Node 0, zone Normal, type Reclaimable 2 2 1 23 13 1 2 1 0 1 0
> Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0
> Unmovable ≈ 15GB
>
> after：
> Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
> …
> Node 0, zone Normal, type Unmovable 0 1 1 0 0 0 0 1 1 1 0
> Node 0, zone Normal, type Movable 1563 4107 1119 189 256 368 286 132 109 4 3841
> Node 0, zone Normal, type Reclaimable 2 2 1 23 13 1 2 1 0 1 0
> Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0
> Node 0, zone Normal, type Isolate 0 0 0 0 0 0 0 0 0 0 0
>
> Signed-off-by: suhua <suhua1@xxxxxxxxxxxx>
> ---
> mm/mm_init.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index 4ba5607aaf19..e0190e3f8f26 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -722,6 +722,12 @@ static void __meminit init_reserved_page(unsigned long pfn, int nid)
> if (zone_spans_pfn(zone, pfn))
> break;
> }
> +
> + if (pageblock_aligned(pfn)) {
> + set_pageblock_migratetype(pfn_to_page(pfn), MIGRATE_MOVABLE);
> + cond_resched();
> + }
If you are trying to make initialization of pageblock migrate type
consistent with or without CONFIG_DEFERRED_STRUCT_PAGE_INIT, move setting
of migrate type from deferred_free_pages() to deferred_init_pages().
> +
> __init_single_page(pfn_to_page(pfn), pfn, zid, nid);
> }
> #else
> --
> 2.34.1
>
--
Sincerely yours,
Mike.
