Merge tag 'mm-stable-2024-01-08-15-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull MM updates from Andrew Morton:
 "Many singleton patches against the MM code. The patch series which are
  included in this merge do the following:

   - Peng Zhang has done some mapletree maintainance work in the series

	'maple_tree: add mt_free_one() and mt_attr() helpers'
	'Some cleanups of maple tree'

   - In the series 'mm: use memmap_on_memory semantics for dax/kmem'
     Vishal Verma has altered the interworking between memory-hotplug
     and dax/kmem so that newly added 'device memory' can more easily
     have its memmap placed within that newly added memory.

   - Matthew Wilcox continues folio-related work (including a few fixes)
     in the patch series

	'Add folio_zero_tail() and folio_fill_tail()'
	'Make folio_start_writeback return void'
	'Fix fault handler's handling of poisoned tail pages'
	'Convert aops->error_remove_page to ->error_remove_folio'
	'Finish two folio conversions'
	'More swap folio conversions'

   - Kefeng Wang has also contributed folio-related work in the series

	'mm: cleanup and use more folio in page fault'

   - Jim Cromie has improved the kmemleak reporting output in the series
     'tweak kmemleak report format'.

   - In the series 'stackdepot: allow evicting stack traces' Andrey
     Konovalov to permits clients (in this case KASAN) to cause eviction
     of no longer needed stack traces.

   - Charan Teja Kalla has fixed some accounting issues in the page
     allocator's atomic reserve calculations in the series 'mm:
     page_alloc: fixes for high atomic reserve caluculations'.

   - Dmitry Rokosov has added to the samples/ dorectory some sample code
     for a userspace memcg event listener application. See the series
     'samples: introduce cgroup events listeners'.

   - Some mapletree maintanance work from Liam Howlett in the series
     'maple_tree: iterator state changes'.

   - Nhat Pham has improved zswap's approach to writeback in the series
     'workload-specific and memory pressure-driven zswap writeback'.

   - DAMON/DAMOS feature and maintenance work from SeongJae Park in the
     series

	'mm/damon: let users feed and tame/auto-tune DAMOS'
	'selftests/damon: add Python-written DAMON functionality tests'
	'mm/damon: misc updates for 6.8'

   - Yosry Ahmed has improved memcg's stats flushing in the series 'mm:
     memcg: subtree stats flushing and thresholds'.

   - In the series 'Multi-size THP for anonymous memory' Ryan Roberts
     has added a runtime opt-in feature to transparent hugepages which
     improves performance by allocating larger chunks of memory during
     anonymous page faults.

   - Matthew Wilcox has also contributed some cleanup and maintenance
     work against eh buffer_head code int he series 'More buffer_head
     cleanups'.

   - Suren Baghdasaryan has done work on Andrea Arcangeli's series
     'userfaultfd move option'. UFFDIO_MOVE permits userspace heap
     compaction algorithms to move userspace's pages around rather than
     UFFDIO_COPY'a alloc/copy/free.

   - Stefan Roesch has developed a 'KSM Advisor', in the series 'mm/ksm:
     Add ksm advisor'. This is a governor which tunes KSM's scanning
     aggressiveness in response to userspace's current needs.

   - Chengming Zhou has optimized zswap's temporary working memory use
     in the series 'mm/zswap: dstmem reuse optimizations and cleanups'.

   - Matthew Wilcox has performed some maintenance work on the writeback
     code, both code and within filesystems. The series is 'Clean up the
     writeback paths'.

   - Andrey Konovalov has optimized KASAN's handling of alloc and free
     stack traces for secondary-level allocators, in the series 'kasan:
     save mempool stack traces'.

   - Andrey also performed some KASAN maintenance work in the series
     'kasan: assorted clean-ups'.

   - David Hildenbrand has gone to town on the rmap code. Cleanups, more
     pte batching, folio conversions and more. See the series 'mm/rmap:
     interface overhaul'.

   - Kinsey Ho has contributed some maintenance work on the MGLRU code
     in the series 'mm/mglru: Kconfig cleanup'.

   - Matthew Wilcox has contributed lruvec page accounting code cleanups
     in the series 'Remove some lruvec page accounting functions'"

* tag 'mm-stable-2024-01-08-15-31' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (361 commits)
  mm, treewide: rename MAX_ORDER to MAX_PAGE_ORDER
  mm, treewide: introduce NR_PAGE_ORDERS
  selftests/mm: add separate UFFDIO_MOVE test for PMD splitting
  selftests/mm: skip test if application doesn't has root privileges
  selftests/mm: conform test to TAP format output
  selftests: mm: hugepage-mmap: conform to TAP format output
  selftests/mm: gup_test: conform test to TAP format output
  mm/selftests: hugepage-mremap: conform test to TAP format output
  mm/vmstat: move pgdemote_* out of CONFIG_NUMA_BALANCING
  mm: zsmalloc: return -ENOSPC rather than -EINVAL in zs_malloc while size is too large
  mm/memcontrol: remove __mod_lruvec_page_state()
  mm/khugepaged: use a folio more in collapse_file()
  slub: use a folio in __kmalloc_large_node
  slub: use folio APIs in free_large_kmalloc()
  slub: use alloc_pages_node() in alloc_slab_page()
  mm: remove inc/dec lruvec page state functions
  mm: ratelimit stat flush from workingset shrinker
  kasan: stop leaking stack trace handles
  mm/mglru: remove CONFIG_TRANSPARENT_HUGEPAGE
  mm/mglru: add dummy pmd_dirty()
  ...

1 files changed, 78 insertions, 19 deletions

diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
index b0cc8243e093..04eb45a2f940 100644
--- a/Documentation/admin-guide/mm/transhuge.rst
+++ b/Documentation/admin-guide/mm/transhuge.rst
@@ -45,10 +45,25 @@ components:
    the two is using hugepages just because of the fact the TLB miss is
    going to run faster.
 
+Modern kernels support "multi-size THP" (mTHP), which introduces the
+ability to allocate memory in blocks that are bigger than a base page
+but smaller than traditional PMD-size (as described above), in
+increments of a power-of-2 number of pages. mTHP can back anonymous
+memory (for example 16K, 32K, 64K, etc). These THPs continue to be
+PTE-mapped, but in many cases can still provide similar benefits to
+those outlined above: Page faults are significantly reduced (by a
+factor of e.g. 4, 8, 16, etc), but latency spikes are much less
+prominent because the size of each page isn't as huge as the PMD-sized
+variant and there is less memory to clear in each page fault. Some
+architectures also employ TLB compression mechanisms to squeeze more
+entries in when a set of PTEs are virtually and physically contiguous
+and approporiately aligned. In this case, TLB misses will occur less
+often.
+
 THP can be enabled system wide or restricted to certain tasks or even
 memory ranges inside task's address space. Unless THP is completely
 disabled, there is ``khugepaged`` daemon that scans memory and
-collapses sequences of basic pages into huge pages.
+collapses sequences of basic pages into PMD-sized huge pages.
 
 The THP behaviour is controlled via :ref:`sysfs <thp_sysfs>`
 interface and using madvise(2) and prctl(2) system calls.
@@ -95,12 +110,40 @@ Global THP controls
 Transparent Hugepage Support for anonymous memory can be entirely disabled
 (mostly for debugging purposes) or only enabled inside MADV_HUGEPAGE
 regions (to avoid the risk of consuming more memory resources) or enabled
-system wide. This can be achieved with one of::
+system wide. This can be achieved per-supported-THP-size with one of::
+
+	echo always >/sys/kernel/mm/transparent_hugepage/hugepages-<size>kB/enabled
+	echo madvise >/sys/kernel/mm/transparent_hugepage/hugepages-<size>kB/enabled
+	echo never >/sys/kernel/mm/transparent_hugepage/hugepages-<size>kB/enabled
+
+where <size> is the hugepage size being addressed, the available sizes
+for which vary by system.
+
+For example::
+
+	echo always >/sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled
+
+Alternatively it is possible to specify that a given hugepage size
+will inherit the top-level "enabled" value::
+
+	echo inherit >/sys/kernel/mm/transparent_hugepage/hugepages-<size>kB/enabled
+
+For example::
+
+	echo inherit >/sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled
+
+The top-level setting (for use with "inherit") can be set by issuing
+one of the following commands::
 
 	echo always >/sys/kernel/mm/transparent_hugepage/enabled
 	echo madvise >/sys/kernel/mm/transparent_hugepage/enabled
 	echo never >/sys/kernel/mm/transparent_hugepage/enabled
 
+By default, PMD-sized hugepages have enabled="inherit" and all other
+hugepage sizes have enabled="never". If enabling multiple hugepage
+sizes, the kernel will select the most appropriate enabled size for a
+given allocation.
+
 It's also possible to limit defrag efforts in the VM to generate
 anonymous hugepages in case they're not immediately free to madvise
 regions or to never try to defrag memory and simply fallback to regular
@@ -146,25 +189,34 @@ madvise
 never
 	should be self-explanatory.
 
-By default kernel tries to use huge zero page on read page fault to
-anonymous mapping. It's possible to disable huge zero page by writing 0
-or enable it back by writing 1::
+By default kernel tries to use huge, PMD-mappable zero page on read
+page fault to anonymous mapping. It's possible to disable huge zero
+page by writing 0 or enable it back by writing 1::
 
 	echo 0 >/sys/kernel/mm/transparent_hugepage/use_zero_page
 	echo 1 >/sys/kernel/mm/transparent_hugepage/use_zero_page
 
-Some userspace (such as a test program, or an optimized memory allocation
-library) may want to know the size (in bytes) of a transparent hugepage::
+Some userspace (such as a test program, or an optimized memory
+allocation library) may want to know the size (in bytes) of a
+PMD-mappable transparent hugepage::
 
 	cat /sys/kernel/mm/transparent_hugepage/hpage_pmd_size
 
-khugepaged will be automatically started when
-transparent_hugepage/enabled is set to "always" or "madvise, and it'll
-be automatically shutdown if it's set to "never".
+khugepaged will be automatically started when one or more hugepage
+sizes are enabled (either by directly setting "always" or "madvise",
+or by setting "inherit" while the top-level enabled is set to "always"
+or "madvise"), and it'll be automatically shutdown when the last
+hugepage size is disabled (either by directly setting "never", or by
+setting "inherit" while the top-level enabled is set to "never").
 
 Khugepaged controls
 -------------------
 
+.. note::
+   khugepaged currently only searches for opportunities to collapse to
+   PMD-sized THP and no attempt is made to collapse to other THP
+   sizes.
+
 khugepaged runs usually at low frequency so while one may not want to
 invoke defrag algorithms synchronously during the page faults, it
 should be worth invoking defrag at least in khugepaged. However it's
@@ -282,19 +334,26 @@ force
 Need of application restart
 ===========================
 
-The transparent_hugepage/enabled values and tmpfs mount option only affect
-future behavior. So to make them effective you need to restart any
-application that could have been using hugepages. This also applies to the
-regions registered in khugepaged.
+The transparent_hugepage/enabled and
+transparent_hugepage/hugepages-<size>kB/enabled values and tmpfs mount
+option only affect future behavior. So to make them effective you need
+to restart any application that could have been using hugepages. This
+also applies to the regions registered in khugepaged.
 
 Monitoring usage
 ================
 
-The number of anonymous transparent huge pages currently used by the
+.. note::
+   Currently the below counters only record events relating to
+   PMD-sized THP. Events relating to other THP sizes are not included.
+
+The number of PMD-sized anonymous transparent huge pages currently used by the
 system is available by reading the AnonHugePages field in ``/proc/meminfo``.
-To identify what applications are using anonymous transparent huge pages,
-it is necessary to read ``/proc/PID/smaps`` and count the AnonHugePages fields
-for each mapping.
+To identify what applications are using PMD-sized anonymous transparent huge
+pages, it is necessary to read ``/proc/PID/smaps`` and count the AnonHugePages
+fields for each mapping. (Note that AnonHugePages only applies to traditional
+PMD-sized THP for historical reasons and should have been called
+AnonHugePmdMapped).
 
 The number of file transparent huge pages mapped to userspace is available
 by reading ShmemPmdMapped and ShmemHugePages fields in ``/proc/meminfo``.
@@ -413,7 +472,7 @@ for huge pages.
 Optimizing the applications
 ===========================
 
-To be guaranteed that the kernel will map a 2M page immediately in any
+To be guaranteed that the kernel will map a THP immediately in any
 memory region, the mmap region has to be hugepage naturally
 aligned. posix_memalign() can provide that guarantee.