Lines Matching +full:two +full:- +full:user
1 .. SPDX-License-Identifier: GPL-2.0
13 The monitoring-related information including the monitoring request
14 specification and DAMON-based operation schemes are stored in a data structure
19 To know how user-space can do the configurations and start/stop DAMON, refer to
28 - :ref:`Operations Set <damon_operations_set>`: Implements fundamental
30 address-space and available set of software/hardware primitives,
31 - :ref:`Core <damon_core_logic>`: Implements core logics including monitoring
32 overhead/accuracy control and access-aware system operations on top of the
34 - :ref:`Modules <damon_modules>`: Implements kernel modules for various
35 purposes that provides interfaces for the user space, on top of the core
48 the given target address space. For example, below two operations for access
49 monitoring are address-space dependent.
70 DAMON currently provides below three operation sets. Below two subsections
73 - vaddr: Monitor virtual address spaces of specific processes
74 - fvaddr: Monitor fixed virtual address ranges
75 - paddr: Monitor the physical address space of the system
77 To know how user-space can do the configuration via :ref:`DAMON sysfs interface
84 VMA-based Target Address Range Construction
85 -------------------------------------------
95 Only small parts in the super-huge virtual address space of the processes are
104 distinct regions that cover every mapped area of the address space. The two
105 gaps between the three regions are the two biggest unmapped areas in the given
106 address space. The two biggest unmapped areas would be the gap between the
107 heap and the uppermost mmap()-ed region, and the gap between the lowermost
108 mmap()-ed region and the stack in most of the cases. Because these gaps are
110 to make a reasonable trade-off. Below shows this in detail::
114 <uppermost mmap()-ed region>
115 (small mmap()-ed regions and munmap()-ed regions)
116 <lowermost mmap()-ed region>
121 PTE Accessed-bit Based Access Check
122 -----------------------------------
125 Accessed-bit for basic access checks. Only one difference is the way of
147 ----------
154 To know how user-space can set the attributes via :ref:`DAMON sysfs interface
169 clears the results. This can be described in below simple pseudo-code::
200 minimum and the maximum number of regions for the trade-off.
219 sum of the two regions' sizes is smaller than the size of total regions divided
220 by the ``minimum number of regions``, DAMON merges the two regions. If the
223 threshold until the upper-limit of the number of regions is met, or the
226 aggregated access frequency of each region, it splits each region into two or
227 three regions if the total number of regions will not exceed the user-specified
230 In this way, DAMON provides its best-effort quality and minimal overhead while
231 keeping the bounds users set for their trade-off.
255 be hot-plugged.
259 and applies it to monitoring operations-related data structures such as the
260 abstracted monitoring target memory area only for each of a user-specified time
263 User-space can get the monitoring results via DAMON sysfs interface and/or
289 making only rare accesses but the user thinks the amount of accesses for the
298 intensiveness of the workload. The user should tune the interval based on the
327 -----------------
329 One common purpose of data access monitoring is access-aware system efficiency
332 paging out memory regions that are not accessed for more than two minutes
339 One straightforward approach for such schemes would be profile-guided
352 including monitoring results and operation advice between kernel and user
356 works, DAMON provides a feature called Data Access Monitoring-based Operation
359 the access pattern of interest, and applies the user-desired operation actions
360 to the regions, for every user-specified time interval called
363 To know how user-space can set ``apply_interval`` via :ref:`DAMON sysfs
390 - ``willneed``: Call ``madvise()`` for the region with ``MADV_WILLNEED``.
392 - ``cold``: Call ``madvise()`` for the region with ``MADV_COLD``.
394 - ``pageout``: Reclaim the region.
396 - ``hugepage``: Call ``madvise()`` for the region with ``MADV_HUGEPAGE``.
398 - ``nohugepage``: Call ``madvise()`` for the region with ``MADV_NOHUGEPAGE``.
400 - ``lru_prio``: Prioritize the region on its LRU lists.
402 - ``lru_deprio``: Deprioritize the region on its LRU lists.
404 - ``migrate_hot``: Migrate the regions prioritizing warmer regions.
406 - ``migrate_cold``: Migrate the regions prioritizing colder regions.
408 - ``stat``: Do nothing but count the statistics.
415 To know how user-space can set the action via :ref:`DAMON sysfs interface
432 To know how user-space can set the access pattern via :ref:`DAMON sysfs
442 DAMOS upper-bound overhead control feature. DAMOS could incur high overhead if
450 To mitigate that situation, DAMOS provides an upper-bound overhead control
453 the action can be applied within a user-specified time duration.
455 To know how user-space can set the basic quotas via :ref:`DAMON sysfs interface
471 rarely accessed (colder) memory regions would be prioritized for page-out
486 To know how user-space can set the prioritization weights via :ref:`DAMON sysfs
493 Aim-oriented Feedback-driven Auto-tuning
496 Automatic feedback-driven quota tuning. Instead of setting the absolute quota
504 ``target_value``, and ``current_value``. The auto-tuning mechanism tries to
506 Currently, two ``target_metric`` are provided.
508 - ``user_input``: User-provided value. Users could use any metric that they
514 - ``some_mem_psi_us``: System-wide ``some`` memory pressure stall information
517 set by users at the initial time. In other words, DAMOS does self-feedback.
519 To know how user-space can set the tuning goal metric, the target value, and/or
532 consume unnecessary system resources. To avoid such consumption, the user would
545 To know how user-space can set the watermarks via :ref:`DAMON sysfs interface
555 Non-access pattern-based target memory regions filtering. If users run
556 self-written programs or have good profiling tools, they could know something
560 have a list of latency-critical processes.
566 - a type of memory (``type``),
567 - whether it is for the memory of the type or all except the type
569 - whether it is to allow (include) or reject (exclude) applying
582 young or not, since it matches with the first allow-filter. If the page is
584 second reject-filter blocks it. If the page is neither anonymous nor young,
589 filter-allowed or filters evaluation stage passed. It means that installing
590 allow-filters at the end of the list makes no practical change but only
591 filters-checking overhead.
596 case of the core layer-handled filters, the memory regions that excluded by the
598 a memory regions is filtered by an operations set layer-handled filter, it is
603 - anonymous page
604 - Applied to pages that containing data that not stored in files.
605 - Handled by operations set layer. Supported by only ``paddr`` set.
606 - memory cgroup
607 - Applied to pages that belonging to a given cgroup.
608 - Handled by operations set layer. Supported by only ``paddr`` set.
609 - young page
610 - Applied to pages that are accessed after the last access check from the
612 - Handled by operations set layer. Supported by only ``paddr`` set.
613 - address range
614 - Applied to pages that belonging to a given address range.
615 - Handled by the core logic.
616 - DAMON monitoring target
617 - Applied to pages that belonging to a given DAMON monitoring target.
618 - Handled by the core logic.
620 To know how user-space can set the watermarks via :ref:`DAMON sysfs interface
635 - ``nr_tried``: Total number of regions that the scheme is tried to be applied.
636 - ``sz_trtied``: Total size of regions that the scheme is tried to be applied.
637 - ``sz_ops_filter_passed``: Total bytes that passed operations set
638 layer-handled DAMOS filters.
639 - ``nr_applied``: Total number of regions that the scheme is applied.
640 - ``sz_applied``: Total size of regions that the scheme is applied.
641 - ``qt_exceeds``: Total number of times the quota of the scheme has exceeded.
663 To know how user-space can read the stats via :ref:`DAMON sysfs interface
680 ---------------------------------
682 The programming interface for kernel space data access-aware applications.
685 access-aware applications using DAMON's core features. For this, DAMON exposes
697 provide any direct interface for the user space. Such interfaces should be
698 implemented by each DAMON API user kernel components, instead. DAMON subsystem
699 itself implements such DAMON API user modules, which are supposed to be used
700 for general purpose DAMON control and special purpose data access-aware system
702 user space. The user space can build their efficient data access-aware
706 General Purpose User Interface Modules
707 --------------------------------------
709 DAMON modules that provide user space ABIs for general purpose DAMON usage in
715 DAMON user interface modules control DAMON and retrieve the results as user
716 requested via the DAMON API, and return the results to the user-space.
718 The ABIs are designed to be used for user space applications development,
720 user space tools. One such Python-written user space tool is available at
723 (https://packages.fedoraproject.org/pkgs/python-damo/damo/).
730 Special-Purpose Access-aware Kernel Modules
731 -------------------------------------------
733 DAMON modules that provide user space ABI for specific purpose DAMON usage.
735 DAMON user interface modules are for full control of all DAMON features in
736 runtime. For each special-purpose system-wide data access-aware system
739 extended for boot-time and even compile time control. Default values of DAMON
743 To support such cases, yet more DAMON API user kernel modules that provide more
744 simple and optimized user space interfaces are available. Currently, two
747 (:doc:`/admin-guide/mm/damon/reclaim` and
748 :doc:`/admin-guide/mm/damon/lru_sort`).