diff options
Diffstat (limited to 'Documentation/admin-guide/mm/damon')
| -rw-r--r-- | Documentation/admin-guide/mm/damon/index.rst | 3 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/damon/lru_sort.rst | 294 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/damon/reclaim.rst | 8 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/damon/usage.rst | 10 |
4 files changed, 303 insertions, 12 deletions
diff --git a/Documentation/admin-guide/mm/damon/index.rst b/Documentation/admin-guide/mm/damon/index.rst index 61aff88347f3..05500042f777 100644 --- a/Documentation/admin-guide/mm/damon/index.rst +++ b/Documentation/admin-guide/mm/damon/index.rst @@ -4,7 +4,7 @@ Monitoring Data Accesses ======================== -:doc:`DAMON </vm/damon/index>` allows light-weight data access monitoring. +:doc:`DAMON </mm/damon/index>` allows light-weight data access monitoring. Using DAMON, users can analyze the memory access patterns of their systems and optimize those. @@ -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 46306f1f34b1..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 @@ -268,4 +262,4 @@ granularity reclamation. :: .. [1] https://research.google/pubs/pub48551/ .. [2] https://lwn.net/Articles/787611/ -.. [3] https://www.kernel.org/doc/html/latest/vm/free_page_reporting.html +.. [3] https://www.kernel.org/doc/html/latest/mm/free_page_reporting.html diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst index 1bb7b72414b2..d52f572a9029 100644 --- a/Documentation/admin-guide/mm/damon/usage.rst +++ b/Documentation/admin-guide/mm/damon/usage.rst @@ -30,11 +30,11 @@ DAMON provides below interfaces for different users. <sysfs_interface>`. This will be removed after next LTS kernel is released, so users should move to the :ref:`sysfs interface <sysfs_interface>`. - *Kernel Space Programming Interface.* - :doc:`This </vm/damon/api>` is for kernel space programmers. Using this, + :doc:`This </mm/damon/api>` is for kernel space programmers. Using this, users can utilize every feature of DAMON most flexibly and efficiently by writing kernel space DAMON application programs for you. You can even extend DAMON for various address spaces. For detail, please refer to the interface - :doc:`document </vm/damon/api>`. + :doc:`document </mm/damon/api>`. .. _sysfs_interface: @@ -185,7 +185,7 @@ controls the monitoring overhead, exist. You can set and get the values by writing to and rading from the files. For more details about the intervals and monitoring regions range, please refer -to the Design document (:doc:`/vm/damon/design`). +to the Design document (:doc:`/mm/damon/design`). contexts/<N>/targets/ --------------------- @@ -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/ @@ -402,7 +404,7 @@ Attributes Users can get and set the ``sampling interval``, ``aggregation interval``, ``update interval``, and min/max number of monitoring target regions by reading from and writing to the ``attrs`` file. To know about the monitoring -attributes in detail, please refer to the :doc:`/vm/damon/design`. For +attributes in detail, please refer to the :doc:`/mm/damon/design`. For example, below commands set those values to 5 ms, 100 ms, 1,000 ms, 10 and 1000, and then check it again:: |