Hi Mike
Thanks for your advice and sorry for taking so long to reply.
I looked at the logic again. deferred_init_pages is currently used to
handle all (memory &&! reserved) area memblock，and put that memory in
buddy.
Change it to also handle reserved memory may involve more code
changes. I wonder if I can change the commit message: This patch is
mainly to
make the migration type to MIGRATE_MOVABLE when the reserve type page
is initialized, regardless of whether CONFIG_DEFERRED_STRUCT_PAGE_INIT
is set or not?
When not set CONFIG_DEFERRED_STRUCT_PAGE_INIT， initializes memblock of
reserve type to MIGRATE_MOVABLE by default at memmap_init initializes
memory.
Sincerely yours，
Su
Mike Rapoport <rppt@xxxxxxxxxx> 于2024年9月29日周日 17:18写道：
>
> 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.
