diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/procfs-smaps_rollup | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 35 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/damon/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/damon/lru_sort.rst | 294 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/damon/reclaim.rst | 6 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/damon/usage.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/shrinker_debugfs.rst | 135 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/userfaultfd.rst | 40 | ||||
| -rw-r--r-- | Documentation/admin-guide/sysctl/vm.rst | 8 | ||||
| -rw-r--r-- | Documentation/core-api/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/core-api/maple_tree.rst | 217 | ||||
| -rw-r--r-- | Documentation/filesystems/proc.rst | 31 | ||||
| -rw-r--r-- | Documentation/mm/balance.rst | 2 |
14 files changed, 746 insertions, 28 deletions
diff --git a/Documentation/ABI/testing/procfs-smaps_rollup b/Documentation/ABI/testing/procfs-smaps_rollup index a4e31c465194..b446a7154a1b 100644 --- a/Documentation/ABI/testing/procfs-smaps_rollup +++ b/Documentation/ABI/testing/procfs-smaps_rollup @@ -22,6 +22,7 @@ Description: MMUPageSize: 4 kB Rss: 884 kB Pss: 385 kB + Pss_Dirty: 68 kB Pss_Anon: 301 kB Pss_File: 80 kB Pss_Shmem: 4 kB diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 3ebc22e524b0..c408070f30a3 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1667,6 +1667,19 @@ hlt [BUGS=ARM,SH] + hostname= [KNL] Set the hostname (aka UTS nodename). + Format: <string> + This allows setting the system's hostname during early + startup. This sets the name returned by gethostname. + Using this parameter to set the hostname makes it + possible to ensure the hostname is correctly set before + any userspace processes run, avoiding the possibility + that a process may call gethostname before the hostname + has been explicitly set, resulting in the calling + process getting an incorrect result. The string must + not exceed the maximum allowed hostname length (usually + 64 characters) and will be truncated otherwise. + hpet= [X86-32,HPET] option to control HPET usage Format: { enable (default) | disable | force | verbose } @@ -1722,9 +1735,11 @@ Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y, the default is on. - This is not compatible with memory_hotplug.memmap_on_memory. - If both parameters are enabled, hugetlb_free_vmemmap takes - precedence over memory_hotplug.memmap_on_memory. + Note that the vmemmap pages may be allocated from the added + memory block itself when memory_hotplug.memmap_on_memory is + enabled, those vmemmap pages cannot be optimized even if this + feature is enabled. Other vmemmap pages not allocated from + the added memory block itself do not be affected. hung_task_panic= [KNL] Should the hung task detector generate panics. @@ -3083,10 +3098,12 @@ [KNL,X86,ARM] Boolean flag to enable this feature. Format: {on | off (default)} When enabled, runtime hotplugged memory will - allocate its internal metadata (struct pages) - from the hotadded memory which will allow to - hotadd a lot of memory without requiring - additional memory to do so. + allocate its internal metadata (struct pages, + those vmemmap pages cannot be optimized even + if hugetlb_free_vmemmap is enabled) from the + hotadded memory which will allow to hotadd a + lot of memory without requiring additional + memory to do so. This feature is disabled by default because it has some implication on large (e.g. GB) allocations in some configurations (e.g. small @@ -3096,10 +3113,6 @@ Note that even when enabled, there are a few cases where the feature is not effective. - This is not compatible with hugetlb_free_vmemmap. If - both parameters are enabled, hugetlb_free_vmemmap takes - precedence over memory_hotplug.memmap_on_memory. - memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest Format: <integer> default : 0 <disable> diff --git a/Documentation/admin-guide/mm/damon/index.rst b/Documentation/admin-guide/mm/damon/index.rst index c4681fa69b9c..05500042f777 100644 --- a/Documentation/admin-guide/mm/damon/index.rst +++ b/Documentation/admin-guide/mm/damon/index.rst @@ -14,3 +14,4 @@ optimize those. start usage reclaim + lru_sort diff --git a/Documentation/admin-guide/mm/damon/lru_sort.rst b/Documentation/admin-guide/mm/damon/lru_sort.rst new file mode 100644 index 000000000000..c09cace80651 --- /dev/null +++ b/Documentation/admin-guide/mm/damon/lru_sort.rst @@ -0,0 +1,294 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================= +DAMON-based LRU-lists Sorting +============================= + +DAMON-based LRU-lists Sorting (DAMON_LRU_SORT) is a static kernel module that +aimed to be used for proactive and lightweight data access pattern based +(de)prioritization of pages on their LRU-lists for making LRU-lists a more +trusworthy data access pattern source. + +Where Proactive LRU-lists Sorting is Required? +============================================== + +As page-granularity access checking overhead could be significant on huge +systems, LRU lists are normally not proactively sorted but partially and +reactively sorted for special events including specific user requests, system +calls and memory pressure. As a result, LRU lists are sometimes not so +perfectly prepared to be used as a trustworthy access pattern source for some +situations including reclamation target pages selection under sudden memory +pressure. + +Because DAMON can identify access patterns of best-effort accuracy while +inducing only user-specified range of overhead, proactively running +DAMON_LRU_SORT could be helpful for making LRU lists more trustworthy access +pattern source with low and controlled overhead. + +How It Works? +============= + +DAMON_LRU_SORT finds hot pages (pages of memory regions that showing access +rates that higher than a user-specified threshold) and cold pages (pages of +memory regions that showing no access for a time that longer than a +user-specified threshold) using DAMON, and prioritizes hot pages while +deprioritizing cold pages on their LRU-lists. To avoid it consuming too much +CPU for the prioritizations, a CPU time usage limit can be configured. Under +the limit, it prioritizes and deprioritizes more hot and cold pages first, +respectively. System administrators can also configure under what situation +this scheme should automatically activated and deactivated with three memory +pressure watermarks. + +Its default parameters for hotness/coldness thresholds and CPU quota limit are +conservatively chosen. That is, the module under its default parameters could +be widely used without harm for common situations while providing a level of +benefits for systems having clear hot/cold access patterns under memory +pressure while consuming only a limited small portion of CPU time. + +Interface: Module Parameters +============================ + +To use this feature, you should first ensure your system is running on a kernel +that is built with ``CONFIG_DAMON_LRU_SORT=y``. + +To let sysadmins enable or disable it and tune for the given system, +DAMON_LRU_SORT utilizes module parameters. That is, you can put +``damon_lru_sort.<parameter>=<value>`` on the kernel boot command line or write +proper values to ``/sys/modules/damon_lru_sort/parameters/<parameter>`` files. + +Below are the description of each parameter. + +enabled +------- + +Enable or disable DAMON_LRU_SORT. + +You can enable DAMON_LRU_SORT by setting the value of this parameter as ``Y``. +Setting it as ``N`` disables DAMON_LRU_SORT. Note that DAMON_LRU_SORT could do +no real monitoring and LRU-lists sorting due to the watermarks-based activation +condition. Refer to below descriptions for the watermarks parameter for this. + +commit_inputs +------------- + +Make DAMON_LRU_SORT reads the input parameters again, except ``enabled``. + +Input parameters that updated while DAMON_LRU_SORT is running are not applied +by default. Once this parameter is set as ``Y``, DAMON_LRU_SORT reads values +of parametrs except ``enabled`` again. Once the re-reading is done, this +parameter is set as ``N``. If invalid parameters are found while the +re-reading, DAMON_LRU_SORT will be disabled. + +hot_thres_access_freq +--------------------- + +Access frequency threshold for hot memory regions identification in permil. + +If a memory region is accessed in frequency of this or higher, DAMON_LRU_SORT +identifies the region as hot, and mark it as accessed on the LRU list, so that +it could not be reclaimed under memory pressure. 50% by default. + +cold_min_age +------------ + +Time threshold for cold memory regions identification in microseconds. + +If a memory region is not accessed for this or longer time, DAMON_LRU_SORT +identifies the region as cold, and mark it as unaccessed on the LRU list, so +that it could be reclaimed first under memory pressure. 120 seconds by +default. + +quota_ms +-------- + +Limit of time for trying the LRU lists sorting in milliseconds. + +DAMON_LRU_SORT tries to use only up to this time within a time window +(quota_reset_interval_ms) for trying LRU lists sorting. This can be used +for limiting CPU consumption of DAMON_LRU_SORT. If the value is zero, the +limit is disabled. + +10 ms by default. + +quota_reset_interval_ms +----------------------- + +The time quota charge reset interval in milliseconds. + +The charge reset interval for the quota of time (quota_ms). That is, +DAMON_LRU_SORT does not try LRU-lists sorting for more than quota_ms +milliseconds or quota_sz bytes within quota_reset_interval_ms milliseconds. + +1 second by default. + +wmarks_interval +--------------- + +The watermarks check time interval in microseconds. + +Minimal time to wait before checking the watermarks, when DAMON_LRU_SORT is +enabled but inactive due to its watermarks rule. 5 seconds by default. + +wmarks_high +----------- + +Free memory rate (per thousand) for the high watermark. + +If free memory of the system in bytes per thousand bytes is higher than this, +DAMON_LRU_SORT becomes inactive, so it does nothing but periodically checks the +watermarks. 200 (20%) by default. + +wmarks_mid +---------- + +Free memory rate (per thousand) for the middle watermark. + +If free memory of the system in bytes per thousand bytes is between this and +the low watermark, DAMON_LRU_SORT becomes active, so starts the monitoring and +the LRU-lists sorting. 150 (15%) by default. + +wmarks_low +---------- + +Free memory rate (per thousand) for the low watermark. + +If free memory of the system in bytes per thousand bytes is lower than this, +DAMON_LRU_SORT becomes inactive, so it does nothing but periodically checks the +watermarks. 50 (5%) by default. + +sample_interval +--------------- + +Sampling interval for the monitoring in microseconds. + +The sampling interval of DAMON for the cold memory monitoring. Please refer to +the DAMON documentation (:doc:`usage`) for more detail. 5ms by default. + +aggr_interval +------------- + +Aggregation interval for the monitoring in microseconds. + +The aggregation interval of DAMON for the cold memory monitoring. Please +refer to the DAMON documentation (:doc:`usage`) for more detail. 100ms by +default. + +min_nr_regions +-------------- + +Minimum number of monitoring regions. + +The minimal number of monitoring regions of DAMON for the cold memory +monitoring. This can be used to set lower-bound of the monitoring quality. +But, setting this too high could result in increased monitoring overhead. +Please refer to the DAMON documentation (:doc:`usage`) for more detail. 10 by +default. + +max_nr_regions +-------------- + +Maximum number of monitoring regions. + +The maximum number of monitoring regions of DAMON for the cold memory +monitoring. This can be used to set upper-bound of the monitoring overhead. +However, setting this too low could result in bad monitoring quality. Please +refer to the DAMON documentation (:doc:`usage`) for more detail. 1000 by +defaults. + +monitor_region_start +-------------------- + +Start of target memory region in physical address. + +The start physical address of memory region that DAMON_LRU_SORT will do work +against. By default, biggest System RAM is used as the region. + +monitor_region_end +------------------ + +End of target memory region in physical address. + +The end physical address of memory region that DAMON_LRU_SORT will do work +against. By default, biggest System RAM is used as the region. + +kdamond_pid +----------- + +PID of the DAMON thread. + +If DAMON_LRU_SORT is enabled, this becomes the PID of the worker thread. Else, +-1. + +nr_lru_sort_tried_hot_regions +----------------------------- + +Number of hot memory regions that tried to be LRU-sorted. + +bytes_lru_sort_tried_hot_regions +-------------------------------- + +Total bytes of hot memory regions that tried to be LRU-sorted. + +nr_lru_sorted_hot_regions +------------------------- + +Number of hot memory regions that successfully be LRU-sorted. + +bytes_lru_sorted_hot_regions +---------------------------- + +Total bytes of hot memory regions that successfully be LRU-sorted. + +nr_hot_quota_exceeds +-------------------- + +Number of times that the time quota limit for hot regions have exceeded. + +nr_lru_sort_tried_cold_regions +------------------------------ + +Number of cold memory regions that tried to be LRU-sorted. + +bytes_lru_sort_tried_cold_regions +--------------------------------- + +Total bytes of cold memory regions that tried to be LRU-sorted. + +nr_lru_sorted_cold_regions +-------------------------- + +Number of cold memory regions that successfully be LRU-sorted. + +bytes_lru_sorted_cold_regions +----------------------------- + +Total bytes of cold memory regions that successfully be LRU-sorted. + +nr_cold_quota_exceeds +--------------------- + +Number of times that the time quota limit for cold regions have exceeded. + +Example +======= + +Below runtime example commands make DAMON_LRU_SORT to find memory regions +having >=50% access frequency and LRU-prioritize while LRU-deprioritizing +memory regions that not accessed for 120 seconds. The prioritization and +deprioritization is limited to be done using only up to 1% CPU time to avoid +DAMON_LRU_SORT consuming too much CPU time for the (de)prioritization. It also +asks DAMON_LRU_SORT to do nothing if the system's free memory rate is more than +50%, but start the real works if it becomes lower than 40%. If DAMON_RECLAIM +doesn't make progress and therefore the free memory rate becomes lower than +20%, it asks DAMON_LRU_SORT to do nothing again, so that we can fall back to +the LRU-list based page granularity reclamation. :: + + # cd /sys/modules/damon_lru_sort/parameters + # echo 500 > hot_thres_access_freq + # echo 120000000 > cold_min_age + # echo 10 > quota_ms + # echo 1000 > quota_reset_interval_ms + # echo 500 > wmarks_high + # echo 400 > wmarks_mid + # echo 200 > wmarks_low + # echo Y > enabled diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst index a8bd3bd29959..4f1479a11e63 100644 --- a/Documentation/admin-guide/mm/damon/reclaim.rst +++ b/Documentation/admin-guide/mm/damon/reclaim.rst @@ -48,12 +48,6 @@ DAMON_RECLAIM utilizes module parameters. That is, you can put ``damon_reclaim.<parameter>=<value>`` on the kernel boot command line or write proper values to ``/sys/modules/damon_reclaim/parameters/<parameter>`` files. -Note that the parameter values except ``enabled`` are applied only when -DAMON_RECLAIM starts. Therefore, if you want to apply new parameter values in -runtime and DAMON_RECLAIM is already enabled, you should disable and re-enable -it via ``enabled`` parameter file. Writing of the new values to proper -parameter values should be done before the re-enablement. - Below are the description of each parameter. enabled diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst index 5540a3a40fc9..d52f572a9029 100644 --- a/Documentation/admin-guide/mm/damon/usage.rst +++ b/Documentation/admin-guide/mm/damon/usage.rst @@ -264,6 +264,8 @@ that can be written to and read from the file and their meaning are as below. - ``pageout``: Call ``madvise()`` for the region with ``MADV_PAGEOUT`` - ``hugepage``: Call ``madvise()`` for the region with ``MADV_HUGEPAGE`` - ``nohugepage``: Call ``madvise()`` for the region with ``MADV_NOHUGEPAGE`` + - ``lru_prio``: Prioritize the region on its LRU lists. + - ``lru_deprio``: Deprioritize the region on its LRU lists. - ``stat``: Do nothing but count the statistics schemes/<N>/access_pattern/ diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst index c21b5823f126..1bd11118dfb1 100644 --- a/Documentation/admin-guide/mm/index.rst +++ b/Documentation/admin-guide/mm/index.rst @@ -36,6 +36,7 @@ the Linux memory management. numa_memory_policy numaperf pagemap + shrinker_debugfs soft-dirty swap_numa transhuge diff --git a/Documentation/admin-guide/mm/shrinker_debugfs.rst b/Documentation/admin-guide/mm/shrinker_debugfs.rst new file mode 100644 index 000000000000..3887f0b294fe --- /dev/null +++ b/Documentation/admin-guide/mm/shrinker_debugfs.rst @@ -0,0 +1,135 @@ +.. _shrinker_debugfs: + +========================== +Shrinker Debugfs Interface +========================== + +Shrinker debugfs interface provides a visibility into the kernel memory +shrinkers subsystem and allows to get information about individual shrinkers +and interact with them. + +For each shrinker registered in the system a directory in **<debugfs>/shrinker/** +is created. The directory's name is composed from the shrinker's name and an +unique id: e.g. *kfree_rcu-0* or *sb-xfs:vda1-36*. + +Each shrinker directory contains **count** and **scan** files, which allow to +trigger *count_objects()* and *scan_objects()* callbacks for each memcg and +numa node (if applicable). + +Usage: +------ + +1. *List registered shrinkers* + + :: + + $ cd /sys/kernel/debug/shrinker/ + $ ls + dquota-cache-16 sb-devpts-28 sb-proc-47 sb-tmpfs-42 + mm-shadow-18 sb-devtmpfs-5 sb-proc-48 sb-tmpfs-43 + mm-zspool:zram0-34 sb-hugetlbfs-17 sb-pstore-31 sb-tmpfs-44 + rcu-kfree-0 sb-hugetlbfs-33 sb-rootfs-2 sb-tmpfs-49 + sb-aio-20 sb-iomem-12 sb-securityfs-6 sb-tracefs-13 + sb-anon_inodefs-15 sb-mqueue-21 sb-selinuxfs-22 sb-xfs:vda1-36 + sb-bdev-3 sb-nsfs-4 sb-sockfs-8 sb-zsmalloc-19 + sb-bpf-32 sb-pipefs-14 sb-sysfs-26 thp-deferred_split-10 + sb-btrfs:vda2-24 sb-proc-25 sb-tmpfs-1 thp-zero-9 + sb-cgroup2-30 sb-proc-39 sb-tmpfs-27 xfs-buf:vda1-37 + sb-configfs-23 sb-proc-41 sb-tmpfs-29 xfs-inodegc:vda1-38 + sb-dax-11 sb-proc-45 sb-tmpfs-35 + sb-debugfs-7 sb-proc-46 sb-tmpfs-40 + +2. *Get information about a specific shrinker* + + :: + + $ cd sb-btrfs\:vda2-24/ + $ ls + count scan + +3. *Count objects* + + Each line in the output has the following format:: + + <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ... + <cgroup inode id> <nr of objects on node 0> <nr of objects on node 1> ... + ... + + If there are no objects on all numa nodes, a line is omitted. If there + are no objects at all, the output might be empty. + + If the shrinker is not memcg-aware or CONFIG_MEMCG is off, 0 is printed + as cgroup inode id. If the shrinker is not numa-aware, 0's are printed + for all nodes except the first one. + :: + + $ cat count + 1 224 2 + 21 98 0 + 55 818 10 + 2367 2 0 + 2401 30 0 + 225 13 0 + 599 35 0 + 939 124 0 + 1041 3 0 + 1075 1 0 + 1109 1 0 + 1279 60 0 + 1313 7 0 + 1347 39 0 + 1381 3 0 + 1449 14 0 + 1483 63 0 + 1517 53 0 + 1551 6 0 + 1585 1 0 + 1619 6 0 + 1653 40 0 + 1687 11 0 + 1721 8 0 + 1755 4 0 + 1789 52 0 + 1823 888 0 + 1857 1 0 + 1925 2 0 + 1959 32 0 + 2027 22 0 + 2061 9 0 + 2469 799 0 + 2537 861 0 + 2639 1 0 + 2707 70 0 + 2775 4 0 + 2877 84 0 + 293 1 0 + 735 8 0 + +4. *Scan objects* + + The expected input format:: + + <cgroup inode id> <numa id> <number of objects to scan> + + For a non-memcg-aware shrinker or on a system with no memory + cgrups **0** should be passed as cgroup id. + :: + + $ cd /sys/kernel/debug/shrinker/ + $ cd sb-btrfs\:vda2-24/ + + $ cat count | head -n 5 + 1 212 0 + 21 97 0 + 55 802 5 + 2367 2 0 + 225 13 0 + + $ echo "55 0 200" > scan + + $ cat count | head -n 5 + 1 212 0 + 21 96 0 + 55 752 5 + 2367 2 0 + 225 13 0 diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 6528036093e1..9bae1acd431f 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -17,7 +17,10 @@ of the ``PROT_NONE+SIGSEGV`` trick. Design ====== -Userfaults are delivered and resolved through the ``userfaultfd`` syscall. +Userspace creates a new userfaultfd, initializes it, and registers one or more +regions of virtual memory with it. Then, any page faults which occur within the +region(s) result in a message being delivered to the userfaultfd, notifying +userspace of the fault. The ``userfaultfd`` (aside from registering and unregistering virtual memory ranges) provides two primary functionalities: @@ -34,12 +37,11 @@ The real advantage of userfaults if compared to regular virtual memory management of mremap/mprotect is that the userfaults in all their operations never involve heavyweight structures like vmas (in fact the ``userfaultfd`` runtime load never takes the mmap_lock for writing). - Vmas are not suitable for page- (or hugepage) granular fault tracking when dealing with virtual address spaces that could span Terabytes. Too many vmas would be needed for that. -The ``userfaultfd`` once opened by invoking the syscall, can also be +The ``userfaultfd``, once created, can also be passed using unix domain sockets to a manager process, so the same manager process could handle the userfaults of a multitude of different processes without them being aware about what is going on @@ -50,6 +52,38 @@ is a corner case that would currently return ``-EBUSY``). API === +Creating a userfaultfd +---------------------- + +There are two ways to create a new userfaultfd, each of which provide ways to +restrict access to this functionality (since historically userfaultfds which +handle kernel page faults have been a useful tool for exploiting the kernel). + +The first way, supported by older kernels, is the userfaultfd(2) syscall. +Access to this is controlled in several ways: + +- By default, the userfaultfd will be able to handle kernel page faults. This + can be disabled by passing in UFFD_USER_MODE_ONLY. + +- If vm.unprivileged_userfaultfd is 0, then the caller must *either* have + CAP_SYS_PTRACE, or pass in UFFD_USER_MODE_ONLY. + +- If vm.unprivileged_userfaultfd is 1, then no particular privilege is needed to + use this syscall, even if UFFD_USER_MODE_ONLY is *not* set. + +The second way, added to the kernel more recently, is by opening and issuing a +USERFAULTFD_IOC_NEW ioctl to /dev/userfaultfd. This method yields equivalent +userfaultfds to the userfaultfd(2) syscall; its benefit is in how access to +creating userfaultfds is controlled. + +Access to /dev/userfaultfd is controlled via normal filesystem permissions +(user/group/mode for example), which gives fine grained access to userfaultfd +specifically, without also granting other unrelated privileges at the same time +(as e.g. granting CAP_SYS_PTRACE would do). + +Initializing up a userfaultfd +----------------------------- + When first opened the ``userfaultfd`` must be enabled invoking the ``UFFDIO_API`` ioctl specifying a ``uffdio_api.api`` value set to ``UFFD_API`` (or a later API version) which will specify the ``read/POLLIN`` protocol diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/admin-guide/sysctl/vm.rst index 4a440a7cfeb0..5a810ea6dc77 100644 --- a/Documentation/admin-guide/sysctl/vm.rst +++ b/Documentation/admin-guide/sysctl/vm.rst @@ -565,9 +565,8 @@ See Documentation/admin-guide/mm/hugetlbpage.rst hugetlb_optimize_vmemmap ======================== -This knob is not available when memory_hotplug.memmap_on_memory (kernel parameter) -is configured or the size of 'struct page' (a structure defined in -include/linux/mm_types.h) is not power of two (an unusual system config could +This knob is not available when the size of 'struct page' (a structure defined +in include/linux/mm_types.h) is not power of two (an unusual system config could result in this). Enable (set to 1) or disable (set to 0) the feature of optimizing vmemmap pages @@ -928,6 +927,9 @@ calls without any restrictions. The default value is 0. +An alternative to this sysctl / the userfaultfd(2) syscall is to create +userfaultfds via /dev/userfaultfd. See +Documentation/admin-guide/mm/userfaultfd.rst. user_reserve_kbytes =================== diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst index dc95df462eea..1da6a4fac664 100644 --- a/Documentation/core-api/index.rst +++ b/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 diff --git a/Documentation/core-api/maple_tree.rst b/Documentation/core-api/maple_tree.rst new file mode 100644 index 000000000000..45defcf15da7 --- /dev/null +++ b/Documentation/core-api/maple_tree.rst @@ -0,0 +1,217 @@ +.. SPDX-License-Identifier: GPL-2.0+ + + +========== +Maple Tree +========== + +:Author: Liam R. Howlett + +Overview +======== + +The Maple Tree is a B-Tree data type which is optimized for storing +non-overlapping ranges, including ranges of size 1. The tree was designed to +be simple to use and does not require a user written search method. It +supports iterating over a range of entries and going to the previous or next +entry in a cache-efficient manner. The tree can also be put into an RCU-safe +mode of operation which allows reading and writing concurrently. Writers must +synchronize on a lock, which can be the default spinlock, or the user can set +the lock to an external lock of a different type. + +The Maple Tree maintains a small memory footprint and was designed to use +modern processor cache efficiently. The majority of the users will be able to +use the normal API. An :ref:`maple-tree-advanced-api` exists for more complex +scenarios. The most important usage of the Maple Tree is the tracking of the +virtual memory areas. + +The Maple Tree can store values between ``0`` and ``ULONG_MAX``. The Maple +Tree reserves values with the bottom two bits set to '10' which are below 4096 +(ie 2, 6, 10 .. 4094) for internal use. If the entries may use reserved +entries then the users can convert the entries using xa_mk_value() and convert +them back by calling xa_to_value(). If the user needs to use a reserved +value, then the user can convert the value when using the +:ref:`maple-tree-advanced-api`, but are blocked by the normal API. + +The Maple Tree can also be configured to support searching for a gap of a given +size (or larger). + +Pre-allocating of nodes is also supported using the +:ref:`maple-tree-advanced-api`. This is useful for users who must guarantee a +successful store operation within a given +code segment when allocating cannot be done. Allocations of nodes are +relatively small at around 256 bytes. + +.. _maple-tree-normal-api: + +Normal API +========== + +Start by initialising a maple tree, either with DEFINE_MTREE() for statically +allocated maple trees or mt_init() for dynamically allocated ones. A +freshly-initialised maple tree contains a ``NULL`` pointer for the range ``0`` +- ``ULONG_MAX``. There are currently two types of maple trees supported: the +allocation tree and the regular tree. The regular tree has a higher branching +factor for internal nodes. The allocation tree has a lower branching factor +but allows the user to search for a gap of a given size or larger from either +``0`` upwards or ``ULONG_MAX`` down. An allocation tree can be used by +passing in the ``MT_FLAGS_ALLOC_RANGE`` flag when initialising the tree. + +You can then set entries using mtree_store() or mtree_store_range(). +mtree_store() will overwrite any entry with the new entry and return 0 on +success or an error code otherwise. mtree_store_range() works in the same way +but takes a range. mtree_load() is used to retrieve the entry stored at a +given index. You can use mtree_erase() to erase an entire range by only +knowing one value within that range, or mtree_store() call with an entry of +NULL may be used to partially erase a range or many ranges at once. + +If you want to only store a new entry to a range (or index) if that range is +currently ``NULL``, you can use mtree_insert_range() or mtree_insert() which +return -EEXIST if the range is not empty. + +You can search for an entry from an index upwards by using mt_find(). + +You can walk each entry within a range by calling mt_for_each(). You must +provide a temporary variable to store a cursor. If you want to walk each +element of the tree then ``0`` and ``ULONG_MAX`` may be used as the range. If +the caller is going to hold the lock for the duration of the walk then it is +worth looking at the mas_for_each() API in the :ref:`maple-tree-advanced-api` +section. + +Sometimes it is necessary to ensure the next call to store to a maple tree does +not allocate memory, please see :ref:`maple-tree-advanced-api` for this use case. + +Finally, you can remove all entries from a maple tree by calling +mtree_destroy(). If the maple tree entries are pointers, you may wish to free +the entries first. + +Allocating Nodes +---------------- + +The allocations are handled by the internal tree code. See +:ref:`maple-tree-advanced-alloc` for other options. + +Locking +------- + +You do not have to worry about locking. See :ref:`maple-tree-advanced-locks` +for other options. + +The Maple Tree uses RCU and an internal spinlock to synchronise access: + +Takes RCU read lock: + * mtree_load() + * mt_find() + * mt_for_each() + * mt_next() + * mt_prev() + +Takes ma_lock internally: + * mtree_store() + * mtree_store_range() + * mtree_insert() + * mtree_insert_range() + * mtree_erase() + * mtree_destroy() + * mt_set_in_rcu() + * mt_clear_in_rcu() + +If you want to take advantage of the internal lock to protect the data +structures that you are storing in the Maple Tree, you can call mtree_lock() +before calling mtree_load(), then take a reference count on the object you +have found before calling mtree_unlock(). This will prevent stores from +removing the object from the tree between looking up the object and +incrementing the refcount. You can also use RCU to avoid dereferencing +freed memory, but an explanation of that is beyond the scope of this +document. + +.. _maple-tree-advanced-api: + +Advanced API +============ + +The advanced API offers more flexibility and better performance at the +cost of an interface which can be harder to use and has fewer safeguards. +You must take care of your own locking while using the advanced API. +You can use the ma_lock, RCU or an external lock for protection. +You can mix advanced and normal operations on the same array, as long +as the locking is compatible. The :ref:`maple-tree-normal-api` is implemented +in terms of the advanced API. + +The advanced API is based around the ma_state, this is where the 'mas' +prefix originates. The ma_state struct keeps track of tree operations to make +life easier for both internal and external tree users. + +Initialising the maple tree is the same as in the :ref:`maple-tree-normal-api`. +Please see above. + +The maple state keeps track of the range start and end in mas->index and +mas->last, respectively. + +mas_walk() will walk the tree to the location of mas->index and set the +mas->index and mas->last according to the range for the entry. + +You can set entries using mas_store(). mas_store() will overwrite any entry +with the new entry and return the first existing entry that is overwritten. +The range is passed in as members of the maple state: index and last. + +You can use mas_erase() to erase an entire range by setting index and +last of the maple state to the desired range to erase. This will erase +the first range that is found in that range, set the maple state index +and last as the range that was erased and return the entry that existed +at that location. + +You can walk each entry within a range by using mas_for_each(). If you want +to walk each element of the tree then ``0`` and ``ULONG_MAX`` may be used as +the range. If the lock needs to be periodically dropped, see the locking +section mas_pause(). + +Using a maple state allows mas_next() and mas_prev() to function as if the +tree was a linked list. With such a high branching factor the amortized +performance penalty is outweighed by cache optimization. mas_next() will +return the next entry which occurs after the entry at index. mas_prev() +will return the previous entry which occurs before the entry at index. + +mas_find() will find the first entry which exists at or above index on +the first call, and the next entry from every subsequent calls. + +mas_find_rev() will find the fist entry which exists at or below the last on +the first call, and the previous entry from every subsequent calls. + +If the user needs to yield the lock during an operation, then the maple state +must be paused using mas_pause(). + +There are a few extra interfaces provided when using an allocation tree. +If you wish to search for a gap within a range, then mas_empty_area() +or mas_empty_area_rev() can be used. mas_empty_area() searches for a gap +starting at the lowest index given up to the maximum of the range. +mas_empty_area_rev() searches for a gap starting at the highest index given +and continues downward to the lower bound of the range. + +.. _maple-tree-advanced-alloc: + +Advanced Allocating Nodes +------------------------- + +Allocations are usually handled internally to the tree, however if allocations +need to occur before a write occurs then calling mas_expected_entries() will +allocate the worst-case number of needed nodes to insert the provided number of +ranges. This also causes the tree to enter mass insertion mode. Once +insertions are complete calling mas_destroy() on the maple state will free the +unused allocations. + +.. _maple-tree-advanced-locks: + +Advanced Locking +---------------- + +The maple tree uses a spinlock by default, but external locks can be used for +tree updates as well. To use an external lock, the tree must be initialized +with the ``MT_FLAGS_LOCK_EXTERN flag``, this is usually done with the +MTREE_INIT_EXT() #define, which takes an external lock as an argument. + +Functions and structures +======================== + +.. kernel-doc:: include/linux/maple_tree.h +.. kernel-doc:: lib/maple_tree.c diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 8543a59f288f..47e95dbc820d 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -448,6 +448,7 @@ Memory Area, or VMA) there is a series of lines such as the following:: MMUPageSize: 4 kB Rss: 892 kB Pss: 374 kB + Pss_Dirty: 0 kB Shared_Clean: 892 kB Shared_Dirty: 0 kB Private_Clean: 0 kB @@ -479,7 +480,9 @@ dirty shared and private pages in the mapping. The "proportional set size" (PSS) of a process is the count of pages it has in memory, where each page is divided by the number of processes sharing it. So if a process has 1000 pages all to itself, and 1000 shared with one other -process, its PSS will be 1500. +process, its PSS will be 1500. "Pss_Dirty" is the portion of PSS which +consists of dirty pages. ("Pss_Clean" is not included, but it can be +calculated by subtracting "Pss_Dirty" from "Pss".) Note that even a page which is part of a MAP_SHARED mapping, but has only a single pte mapped, i.e. is currently used by only one process, is accounted @@ -514,8 +517,10 @@ replaced by copy-on-write) part of the underlying shmem object out on swap. "SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this does not take into account swapped out page of underlying shmem objects. "Locked" indicates whether the mapping is locked in memory or not. + "THPeligible" indicates whether the mapping is eligible for allocating THP -pages - 1 if true, 0 otherwise. It just shows the current status. +pages as well as the THP is PMD mappable or not - 1 if true, 0 otherwise. +It just shows the current status. "VmFlags" field deserves a separate description. This member represents the kernel flags associated with the particular virtual memory area in two letter @@ -1886,13 +1891,14 @@ if precise results are needed. 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file --------------------------------------------------------------- This file provides information associated with an opened file. The regular -files have at least four fields -- 'pos', 'flags', 'mnt_id' and 'ino'. +files have at least five fields -- 'pos', 'flags', 'mnt_id', 'ino', and 'size'. + The 'pos' represents the current offset of the opened file in decimal form [see lseek(2) for details], 'flags' denotes the octal O_xxx mask the file has been created with [see open(2) for details] and 'mnt_id' represents mount ID of the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo for details]. 'ino' represents the inode number of -the file. +the file, and 'size' represents the size of the file in bytes. A typical output is:: @@ -1900,11 +1906,15 @@ A typical output is:: flags: 0100002 mnt_id: 19 ino: 63107 + size: 0 All locks associated with a file descriptor are shown in its fdinfo too:: lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF +Files with anonymous inodes have an additional 'path' field which represents +the anonymous file path. + The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags pair provide additional information particular to the objects they represent. @@ -1917,6 +1927,8 @@ Eventfd files flags: 04002 mnt_id: 9 ino: 63107 + size: 0 + path: anon_inode:[eventfd] eventfd-count: 5a where 'eventfd-count' is hex value of a counter. @@ -1930,6 +1942,8 @@ Signalfd files flags: 04002 mnt_id: 9 ino: 63107 + size: 0 + path: anon_inode:[signalfd] sigmask: 0000000000000200 where 'sigmask' is hex value of the signal mask associated @@ -1944,6 +1958,8 @@ Epoll files flags: 02 mnt_id: 9 ino: 63107 + size: 0 + path: anon_inode:[eventpoll] tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7 where 'tfd' is a target file descriptor number in decimal form, @@ -1962,6 +1978,8 @@ For inotify files the format is the following:: flags: 02000000 mnt_id: 9 ino: 63107 + size: 0 + path: anon_inode:inotify inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d where 'wd' is a watch descriptor in decimal form, i.e. a target file @@ -1985,6 +2003,8 @@ For fanotify files the format is:: flags: 02 mnt_id: 9 ino: 63107 + size: 0 + path: anon_inode:[fanotify] fanotify flags:10 event-flags:0 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4 @@ -2010,6 +2030,8 @@ Timerfd files flags: 02 mnt_id: 9 ino: 63107 + size: 0 + path: anon_inode:[timerfd] clockid: 0 ticks: 0 settime flags: 01 @@ -2034,6 +2056,7 @@ DMA Buffer files mnt_id: 9 ino: 63107 size: 32768 + path: /dmabuf: count: 2 exp_name: system-heap diff --git a/Documentation/mm/balance.rst b/Documentation/mm/balance.rst index 6a1fadf3e173..e38e9d83c1c7 100644 --- a/Documentation/mm/balance.rst +++ b/Documentation/mm/balance.rst @@ -6,7 +6,7 @@ Memory Balancing Started Jan 2000 by Kanoj Sarcar <kanoj@sgi.com> -Memory balancing is needed for !__GFP_ATOMIC and !__GFP_KSWAPD_RECLAIM as +Memory balancing is needed for !__GFP_HIGH and !__GFP_KSWAPD_RECLAIM as well as for non __GFP_IO allocations. The first reason why a caller may avoid reclaim is that the caller can not |