This reintroduces a concept removed by: commit d6cb41cc44 ("mm, hugetlb:
remove hugepages_treat_as_movable sysctl")
This sysctl provides flexibility between ZONE_MOVABLE use cases:
1) onlining memory in ZONE_MOVABLE to maintain hotplug compatibility
2) onlining memory in ZONE_MOVABLE to make hugepage allocate reliable
When ZONE_MOVABLE is used to make huge page allocation more reliable,
disallowing gigantic pages memory in this region is pointless. If hotplug
is not a requirement, we can loosen the restrictions to allow 1GB gigantic
pages in ZONE_MOVABLE.
Since 1GB can be difficult to migrate / has impacts on compaction /
defragmentation, we don't enable this by default. Notably, 1GB pages can
only be migrated if another 1GB page is available - so hot-unplug will
fail if such a page cannot be found.
However, since there are scenarios where gigantic pages are migratable, we
should allow use of these on movable regions.
When not valid 1GB is available for migration, hot-unplug will retry
indefinitely (or until interrupted). For example:
echo 0 > node0/hugepages/..-1GB/nr_hugepages # clear node0 1GB pages
echo 1 > node1/hugepages/..-1GB/nr_hugepages # reserve node1 1GB page
./alloc_huge_node1 & # Allocate a 1GB page on node1
./node1_offline & # attempt to offline all node1 memory
echo 1 > node0/hugepages/..-1GB/nr_hugepages # reserve node0 1GB page
In this example, node1_offline will block indefinitely until the final
step, when a node0 1GB page is made available.
Note: Boot-time CMA is not possible for driver-managed hotplug memory, as
CMA requires the memory to be registered as SystemRAM at boot time.
Additionally, 1GB huge pages are not supported by THP.
Link: https://lkml.kernel.org/r/20251221125603.2364174-1-gourry@gourry.net
Signed-off-by: Gregory Price <gourry@gourry.net>
Suggested-by: David Rientjes <rientjes@google.com>
Link: https://lore.kernel.org/all/20180201193132.Hk7vI_xaU%25akpm@linux-foundation.org/
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "David Hildenbrand (Red Hat)" <david@kernel.org>
Cc: Gregory Price <gourry@gourry.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Following the extraction of sysfs code, this patch moves the sysctl
interface implementation into a dedicated file to further improve code
organization and maintainability of the hugetlb subsystem.
The following components are moved to mm/hugetlb_sysctl.c:
- proc_hugetlb_doulongvec_minmax()
- hugetlb_sysctl_handler_common()
- hugetlb_sysctl_handler()
- hugetlb_mempolicy_sysctl_handler() (CONFIG_NUMA)
- hugetlb_overcommit_handler()
- hugetlb_table[] sysctl table definition
- hugetlb_sysctl_init()
The hugetlb_internal.h header file is updated to declare the sysctl
initialization function with proper #ifdef guards for configurations
without CONFIG_SYSCTL support.
The Makefile is updated to compile hugetlb_sysctl.o when CONFIG_HUGETLBFS
is enabled. This refactoring reduces the size of hugetlb.c and logically
separates the sysctl interface from core hugetlb management code.
MAINTAINERS is updated to add new file hugetlb_sysctl.c.
No functional changes are introduced; all code is moved as-is from
hugetlb.c with consistent formatting.
Link: https://lkml.kernel.org/r/5bbee7ab5be71d0bb1aebec38642d7e83526bb7a.1762398359.git.zhuhui@kylinos.cn
Signed-off-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Hui Zhu <zhuhui@kylinos.cn>
Cc: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
