linux-6.15/mm/Kconfig

1 # SPDX-License-Identifier: GPL-2.0-only
33 	  compress them into a dynamically allocated RAM-based memory pool.
72 	  available at the following LWN page:
160 	  zsmalloc is a slab-based memory allocator designed to store
175 	int "Maximum number of physical pages per-zspage"
181 	  that a zmalloc page (zspage) can consist of. The optimal zspage
252 	  specifically-sized allocations with user-controlled contents
256 	  user-controlled allocations. This may very slightly increase
258 	  of extra pages since the bulk of user-controlled allocations
259 	  are relatively long-lived.
274 	  Try running: slabinfo -DA
293 	  normal kmalloc allocation and makes kmalloc randomly pick one based
307 	bool "Page allocator randomization"
310 	  Randomization of the page allocator improves the average
311 	  utilization of a direct-mapped memory-side-cache. See section
314 	  the presence of a memory-side-cache. There are also incidental
315 	  security benefits as it reduces the predictability of page
318 	  order of pages is selected based on cache utilization benefits
334 	  also breaks ancient binaries (including anything libc5 based).
339 	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
354 	  ELF-FDPIC binfmt's brk and stack allocator.
358 	  userspace.  Since that isn't generally a problem on no-MMU systems,
361 	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
382 	  This option is best suited for non-NUMA systems with
398 	  memory hot-plug systems.  This is normal.
402 	  hot-plug and hot-remove.
478 # Keep arch NUMA mapping infrastructure post-init.
534 	  Example kernel usage would be page structs and page tables.
536 	  See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
569 	  sufficient kernel-capable memory (ZONE_NORMAL) must be
570 	  available to allocate page structs to describe ZONE_MOVABLE.
590 # Heavily threaded applications may benefit from splitting the mm-wide
594 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
595 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
596 # SPARC32 allocates multiple pte tables within a single page, and therefore
597 # a per-page lock leads to problems when multiple tables need to be locked
599 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
647 	  reliably. The page allocator relies on compaction heavily and
652 	  linux-mm@kvack.org.
661 # support for free page reporting
663 	bool "Free page reporting"
665 	  Free page reporting allows for the incremental acquisition of
671 # support for page migration
674 	bool "Page migration"
682 	  pages as migration can relocate pages to satisfy a huge page
698 	  HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available
708 	int "Maximum scale factor of PCP (Per-CPU pageset) batch allocate/free"
712 	  In page allocator, PCP (Per-CPU pageset) is refilled and drained in
713 	  batches.  The batch number is scaled automatically to improve page
735 	bool "Enable KSM for page merging"
742 	  the many instances by a single page with that content, so
795 	  allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
804 	  long-term mappings means that the space is wasted.
814 	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
835 	  applications by speeding up page faults during memory
878 	  XXX: For now, swap cluster backing transparent huge page
884 	bool "Read-only THP for filesystems (EXPERIMENTAL)"
888 	  Allow khugepaged to put read-only file-backed pages in THP.
895 	bool "No per-page mapcount (EXPERIMENTAL)"
897 	  Do not maintain per-page mapcounts for pages part of larger
901 	  this information will rely on less-precise per-allocation information
902 	  instead: for example, using the average per-page mapcount in such
903 	  a large allocation instead of the per-page mapcount.
933 # UP and nommu archs use km based percpu allocator
959 	  subsystems to allocate big physically-contiguous blocks of memory.
998 	  soft-dirty bit on pte-s. This bit it set when someone writes
999 	  into a page just as regular dirty bit, but unlike the latter
1002 	  See Documentation/admin-guide/mm/soft-dirty.rst for more details.
1008 	int "Default maximum user stack size for 32-bit processes (MB)"
1013 	  This is the maximum stack size in Megabytes in the VM layout of 32-bit
1039 	  This adds PG_idle and PG_young flags to 'struct page'.  PTE Accessed
1044 	bool "Enable idle page tracking"
1053 	  See Documentation/admin-guide/mm/idle_page_tracking.rst for
1069 	  checking, an architecture-agnostic way to find the stack pointer
1101 	  "device-physical" addresses which is needed for using a DAX
1107 # Helpers to mirror range of the CPU page tables of a process into device page
1146 	  on EXPERT systems.  /proc/vmstat will only show page counts
1157 	bool "Enable infrastructure for get_user_pages()-related unit tests"
1161 	  to make ioctl calls that can launch kernel-based unit tests for
1166 	  the non-_fast variants.
1168 	  There is also a sub-test that allows running dump_page() on any
1170 	  range of user-space addresses. These pages are either pinned via
1203 # struct io_mapping based helper.  Selected by drivers that need them
1217 	  not mapped to other processes and other kernel page tables.
1248 	  handle page faults in userland.
1259 	  file-backed memory types like shmem and hugetlbfs.
1262 # multi-gen LRU {
1264 	bool "Multi-Gen LRU"
1266 	# make sure folio->flags has enough spare bits
1270 	  Documentation/admin-guide/mm/multigen_lru.rst for details.
1276 	  This option enables the multi-gen LRU by default.
1285 	  This option has a per-memcg and per-node memory overhead.
1299 	  Allow per-vma locking during page fault handling.
1302 	  handling page faults instead of taking mmap_lock.
1329           stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss).
1335 	bool "reclaim empty user page table pages"
1340 	  Try to reclaim empty user page table pages in paths other than munmap
1343 	  Note: now only empty user PTE page table pages will be reclaimed.