Merge branch 'mm-everything' of git://git.kernel.org/pub/scm/linux/ke…

…rnel/git/akpm/mm

Documentation/ABI/testing/sysfs-kernel-mm-memory-tiers

@@ -0,0 +1,35 @@
+What:		/sys/devices/virtual/memory_tiering/
+Date:		August 2022
+Contact:	Linux memory management mailing list <linux-mm@kvack.org>
+Description:	A collection of all the memory tiers allocated.
+
+		Individual memory tier details are contained in subdirectories
+		named by the abstract distance of the memory tier.
+
+		/sys/devices/virtual/memory_tiering/memory_tierN/
+
+
+What:		/sys/devices/virtual/memory_tiering/memory_tierN/
+		/sys/devices/virtual/memory_tiering/memory_tierN/nodes
+Date:		August 2022
+Contact:	Linux memory management mailing list <linux-mm@kvack.org>
+Description:	Directory with details of a specific memory tier
+
+		This is the directory containing information about a particular
+		memory tier, memtierN, where N is derived based on abstract distance.
+
+		A smaller value of N implies a higher (faster) memory tier in the
+		hierarchy.
+
+		nodes: NUMA nodes that are part of this memory tier.
+
+
+What:		/sys/devices/virtual/memory_tiering/toptier_nodes
+Date:		August 2022
+Contact:	Linux memory management mailing list <linux-mm@kvack.org>
+Description:	Toptier node mask
+
+		A toptier is defined as the memory tier from which memory promotion
+		is not done by the kernel.
+
+		toptier_nodes: Union of NUMA nodes that are part of each toptier.

Documentation/accounting/delay-accounting.rst

@@ -13,7 +13,7 @@ a) waiting for a CPU (while being runnable)
 b) completion of synchronous block I/O initiated by the task
 c) swapping in pages
 d) memory reclaim
-e) thrashing page cache
+e) thrashing
 f) direct compact
 g) write-protect copy
 

Documentation/admin-guide/mm/damon/index.rst

@@ -1,8 +1,8 @@
 .. SPDX-License-Identifier: GPL-2.0
 
-========================
-Monitoring Data Accesses
-========================
+==========================
+DAMON: Data Access MONitor
+==========================
 
 :doc:`DAMON </mm/damon/index>` allows light-weight data access monitoring.
 Using DAMON, users can analyze the memory access patterns of their systems and

Documentation/admin-guide/mm/damon/start.rst

@@ -29,16 +29,9 @@ called DAMON Operator (DAMO).  It is available at
 https://github.com/awslabs/damo.  The examples below assume that ``damo`` is on
 your ``$PATH``.  It's not mandatory, though.
 
-Because DAMO is using the debugfs interface (refer to :doc:`usage` for the
-detail) of DAMON, you should ensure debugfs is mounted.  Mount it manually as
-below::
-
-    # mount -t debugfs none /sys/kernel/debug/
-
-or append the following line to your ``/etc/fstab`` file so that your system
-can automatically mount debugfs upon booting::
-
-    debugfs /sys/kernel/debug debugfs defaults 0 0
+Because DAMO is using the sysfs interface (refer to :doc:`usage` for the
+detail) of DAMON, you should ensure :doc:`sysfs </filesystems/sysfs>` is
+mounted.
 
 
 Recording Data Access Patterns

Documentation/admin-guide/mm/damon/usage.rst

@@ -393,6 +393,11 @@ the files as above.  Above is only for an example.
 debugfs Interface
 =================
 
+.. note::
+
+  DAMON debugfs interface will be removed after next LTS kernel is released, so
+  users should move to the :ref:`sysfs interface <sysfs_interface>`.
+
 DAMON exports eight files, ``attrs``, ``target_ids``, ``init_regions``,
 ``schemes``, ``monitor_on``, ``kdamond_pid``, ``mk_contexts`` and
 ``rm_contexts`` under its debugfs directory, ``<debugfs>/damon/``.

Documentation/admin-guide/mm/index.rst

@@ -32,6 +32,7 @@ the Linux memory management.
    idle_page_tracking
    ksm
    memory-hotplug
+   multigen_lru
    nommu-mmap
    numa_memory_policy
    numaperf

Documentation/admin-guide/mm/ksm.rst

@@ -184,6 +184,42 @@ The maximum possible ``pages_sharing/pages_shared`` ratio is limited by the
 ``max_page_sharing`` tunable. To increase the ratio ``max_page_sharing`` must
 be increased accordingly.
 
+Monitoring KSM profit
+=====================
+
+KSM can save memory by merging identical pages, but also can consume
+additional memory, because it needs to generate a number of rmap_items to
+save each scanned page's brief rmap information. Some of these pages may
+be merged, but some may not be abled to be merged after being checked
+several times, which are unprofitable memory consumed.
+
+1) How to determine whether KSM save memory or consume memory in system-wide
+   range? Here is a simple approximate calculation for reference::
+
+	general_profit =~ pages_sharing * sizeof(page) - (all_rmap_items) *
+			  sizeof(rmap_item);
+
+   where all_rmap_items can be easily obtained by summing ``pages_sharing``,
+   ``pages_shared``, ``pages_unshared`` and ``pages_volatile``.
+
+2) The KSM profit inner a single process can be similarly obtained by the
+   following approximate calculation::
+
+	process_profit =~ ksm_merging_pages * sizeof(page) -
+			  ksm_rmap_items * sizeof(rmap_item).
+
+   where ksm_merging_pages is shown under the directory ``/proc/<pid>/``,
+   and ksm_rmap_items is shown in ``/proc/<pid>/ksm_stat``.
+
+From the perspective of application, a high ratio of ``ksm_rmap_items`` to
+``ksm_merging_pages`` means a bad madvise-applied policy, so developers or
+administrators have to rethink how to change madvise policy. Giving an example
+for reference, a page's size is usually 4K, and the rmap_item's size is
+separately 32B on 32-bit CPU architecture and 64B on 64-bit CPU architecture.
+so if the ``ksm_rmap_items/ksm_merging_pages`` ratio exceeds 64 on 64-bit CPU
+or exceeds 128 on 32-bit CPU, then the app's madvise policy should be dropped,
+because the ksm profit is approximately zero or negative.
+
 Monitoring KSM events
 =====================
 

Documentation/admin-guide/mm/multigen_lru.rst

@@ -0,0 +1,156 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=============
+Multi-Gen LRU
+=============
+The multi-gen LRU is an alternative LRU implementation that optimizes
+page reclaim and improves performance under memory pressure. Page
+reclaim decides the kernel's caching policy and ability to overcommit
+memory. It directly impacts the kswapd CPU usage and RAM efficiency.
+
+Quick start
+===========
+Build the kernel with the following configurations.
+
+* ``CONFIG_LRU_GEN=y``
+* ``CONFIG_LRU_GEN_ENABLED=y``
+
+All set!
+
+Runtime options
+===============
+``/sys/kernel/mm/lru_gen/`` contains stable ABIs described in the
+following subsections.
+
+Kill switch
+-----------
+``enabled`` accepts different values to enable or disable the
+following components. Its default value depends on
+``CONFIG_LRU_GEN_ENABLED``. All the components should be enabled
+unless some of them have unforeseen side effects. Writing to
+``enabled`` has no effect when a component is not supported by the
+hardware, and valid values will be accepted even when the main switch
+is off.
+
+====== ===============================================================
+Values Components
+====== ===============================================================
+0x0001 The main switch for the multi-gen LRU.
+0x0002 Clearing the accessed bit in leaf page table entries in large
+       batches, when MMU sets it (e.g., on x86). This behavior can
+       theoretically worsen lock contention (mmap_lock). If it is
+       disabled, the multi-gen LRU will suffer a minor performance
+       degradation for workloads that contiguously map hot pages,
+       whose accessed bits can be otherwise cleared by fewer larger
+       batches.
+0x0004 Clearing the accessed bit in non-leaf page table entries as
+       well, when MMU sets it (e.g., on x86). This behavior was not
+       verified on x86 varieties other than Intel and AMD. If it is
+       disabled, the multi-gen LRU will suffer a negligible
+       performance degradation.
+[yYnN] Apply to all the components above.
+====== ===============================================================
+
+E.g.,
+::
+
+    echo y >/sys/kernel/mm/lru_gen/enabled
+    cat /sys/kernel/mm/lru_gen/enabled
+    0x0007
+    echo 5 >/sys/kernel/mm/lru_gen/enabled
+    cat /sys/kernel/mm/lru_gen/enabled
+    0x0005
+
+Thrashing prevention
+--------------------
+Personal computers are more sensitive to thrashing because it can
+cause janks (lags when rendering UI) and negatively impact user
+experience. The multi-gen LRU offers thrashing prevention to the
+majority of laptop and desktop users who do not have ``oomd``.
+
+Users can write ``N`` to ``min_ttl_ms`` to prevent the working set of
+``N`` milliseconds from getting evicted. The OOM killer is triggered
+if this working set cannot be kept in memory. In other words, this
+option works as an adjustable pressure relief valve, and when open, it
+terminates applications that are hopefully not being used.
+
+Based on the average human detectable lag (~100ms), ``N=1000`` usually
+eliminates intolerable janks due to thrashing. Larger values like
+``N=3000`` make janks less noticeable at the risk of premature OOM
+kills.
+
+The default value ``0`` means disabled.
+
+Experimental features
+=====================
+``/sys/kernel/debug/lru_gen`` accepts commands described in the
+following subsections. Multiple command lines are supported, so does
+concatenation with delimiters ``,`` and ``;``.
+
+``/sys/kernel/debug/lru_gen_full`` provides additional stats for
+debugging. ``CONFIG_LRU_GEN_STATS=y`` keeps historical stats from
+evicted generations in this file.
+
+Working set estimation
+----------------------
+Working set estimation measures how much memory an application needs
+in a given time interval, and it is usually done with little impact on
+the performance of the application. E.g., data centers want to
+optimize job scheduling (bin packing) to improve memory utilizations.
+When a new job comes in, the job scheduler needs to find out whether
+each server it manages can allocate a certain amount of memory for
+this new job before it can pick a candidate. To do so, the job
+scheduler needs to estimate the working sets of the existing jobs.
+
+When it is read, ``lru_gen`` returns a histogram of numbers of pages
+accessed over different time intervals for each memcg and node.
+``MAX_NR_GENS`` decides the number of bins for each histogram. The
+histograms are noncumulative.
+::
+
+    memcg  memcg_id  memcg_path
+       node  node_id
+           min_gen_nr  age_in_ms  nr_anon_pages  nr_file_pages
+           ...
+           max_gen_nr  age_in_ms  nr_anon_pages  nr_file_pages
+
+Each bin contains an estimated number of pages that have been accessed
+within ``age_in_ms``. E.g., ``min_gen_nr`` contains the coldest pages
+and ``max_gen_nr`` contains the hottest pages, since ``age_in_ms`` of
+the former is the largest and that of the latter is the smallest.
+
+Users can write ``+ memcg_id node_id max_gen_nr
+[can_swap [force_scan]]`` to ``lru_gen`` to create a new generation
+``max_gen_nr+1``. ``can_swap`` defaults to the swap setting and, if it
+is set to ``1``, it forces the scan of anon pages when swap is off,
+and vice versa. ``force_scan`` defaults to ``1`` and, if it is set to
+``0``, it employs heuristics to reduce the overhead, which is likely
+to reduce the coverage as well.
+
+A typical use case is that a job scheduler writes to ``lru_gen`` at a
+certain time interval to create new generations, and it ranks the
+servers it manages based on the sizes of their cold pages defined by
+this time interval.
+
+Proactive reclaim
+-----------------
+Proactive reclaim induces page reclaim when there is no memory
+pressure. It usually targets cold pages only. E.g., when a new job
+comes in, the job scheduler wants to proactively reclaim cold pages on
+the server it selected to improve the chance of successfully landing
+this new job.
+
+Users can write ``- memcg_id node_id min_gen_nr [swappiness
+[nr_to_reclaim]]`` to ``lru_gen`` to evict generations less than or
+equal to ``min_gen_nr``. Note that ``min_gen_nr`` should be less than
+``max_gen_nr-1`` as ``max_gen_nr`` and ``max_gen_nr-1`` are not fully
+aged and therefore cannot be evicted. ``swappiness`` overrides the
+default value in ``/proc/sys/vm/swappiness``. ``nr_to_reclaim`` limits
+the number of pages to evict.
+
+A typical use case is that a job scheduler writes to ``lru_gen``
+before it tries to land a new job on a server. If it fails to
+materialize enough cold pages because of the overestimation, it
+retries on the next server according to the ranking result obtained
+from the working set estimation step. This less forceful approach
+limits the impacts on the existing jobs.

Documentation/admin-guide/mm/transhuge.rst

@@ -366,10 +366,9 @@ thp_split_pmd
 	page table entry.
 
 thp_zero_page_alloc
-	is incremented every time a huge zero page is
-	successfully allocated. It includes allocations which where
-	dropped due race with other allocation. Note, it doesn't count
-	every map of the huge zero page, only its allocation.
+	is incremented every time a huge zero page used for thp is
+	successfully allocated. Note, it doesn't count every map of
+	the huge zero page, only its allocation.
 
 thp_zero_page_alloc_failed
 	is incremented if kernel fails to allocate

Documentation/admin-guide/sysctl/kernel.rst

@@ -174,6 +174,7 @@ core_pattern
 	%f      	executable filename
 	%E		executable path
 	%c		maximum size of core file by resource limit RLIMIT_CORE
+	%C		CPU the task ran on
 	%<OTHER>	both are dropped
 	========	==========================================
 

Documentation/core-api/index.rst

@@ -36,6 +36,7 @@ Library functionality that is used throughout the kernel.
    kref
    assoc_array
    xarray
+   maple_tree
    idr
    circular-buffers
    rbtree