kernel/linux.git/mm/damon/Kconfig, branch v6.19.5

mm/damon/Kconfig: make DAMON_STAT_ENABLED_DEFAULT depend on DAMON_STAT

2025-09-13T23:55:07+00:00

The DAMON_STAT_ENABLED_DEFAULT option is strongly tied to DAMON_STAT option -- enabling it alone is meaningless. This patch makes DAMON_STAT_ENABLED_DEFAULT depend on DAMON_STAT, ensuring functional consistency. Link: https://lkml.kernel.org/r/20250815092110.811757-1-lienze@kylinos.cn Fixes: 369c415e6073 ("mm/damon: introduce DAMON_STAT module") Signed-off-by: Enze Li Reviewed-by: SeongJae Park Signed-off-by: Andrew Morton

mm/damon: introduce DAMON_STAT module

2025-07-10T05:41:55+00:00

Patch series "mm/damon: introduce DAMON_STAT for simple and practical access monitoring", v2. DAMON-based access monitoring is not simple due to required DAMON control and results visualizations. Introduce a static kernel module for making it simple. The module can be enabled without manual setup and provides access pattern metrics that easy to fetch and understand the practical access pattern information, namely estimated memory bandwidth and memory idle time percentiles. Background and Problems ======================= DAMON can be used for monitoring data access patterns of the system and workloads. Specifically, users can start DAMON to monitor access events on specific address space with fine controls including address ranges to monitor and time intervals between samplings and aggregations. The resulting access information snapshot contains access frequency (nr_accesses) and how long the frequency was kept (age) for each byte. The monitoring usage is not simple and practical enough for production usage. Users should first start DAMON with a number of parameters, and wait until DAMON's monitoring results capture a reasonable amount of the time data (age). In production, such manual start and wait is impractical to capture useful information from a high number of machines in a timely manner. The monitoring result is also too detailed to be used on production environments. The raw results are hard to be aggregated and/or compared for production environments having a large scale of time, space and machines fleet. Users have to implement and use their own automation of DAMON control and results processing. It is repetitive and challenging since there is no good reference or guideline for such automation. Solution: DAMON_STAT ==================== Implement such automation in kernel space as a static kernel module, namely DAMON_STAT. It can be enabled at build, boot, or run time via its build configuration or module parameter. It monitors the entire physical address space with monitoring intervals that auto-tuned for a reasonable amount of access observations and minimum overhead. It converts the raw monitoring results into simpler metrics that can easily be aggregated and compared, namely estimated memory bandwidth and idle time percentiles. Understanding of the metrics and the user interface of DAMON_STAT is essential. Refer to the commit messages of the second and the third patches of this patch series for more details about the metrics. For the user interface, the standard module parameters system is used. Refer to the fourth patch of this patch series for details of the user interface. Discussions =========== The module aims to be useful on production environments constructed with a large number of machines that run a long time. The auto-tuned monitoring intervals ensure a reasonable quality of the outputs. The auto-tuning also ensures its overhead be reasonable and low enough to be enabled always on the production. The simplified monitoring results metrics can be useful for showing both coldness (idle time percentiles) and hotness (memory bandwidth) of the system's access pattern. We expect the information can be useful for assessing system memory utilization and inspiring optimizations or investigations on both kernel and user space memory management logics for large scale fleets. We hence expect the module is good enough to be just used in most environments. For special cases that require a custom access monitoring automation, users will still benefit by using DAMON_STAT as a reference or a guideline for their specialized automation. This patch (of 4): To use DAMON for monitoring access patterns of the system, users should manually start DAMON via DAMON sysfs ABI with a number of parameters for specifying the monitoring target address space, address ranges, and monitoring intervals. After that, users should also wait until desired amount of time data is captured into DAMON's monitoring results. It is bothersome and take a long time to be practical for access monitoring on large fleet level production environments. For access-aware system operations use cases like proactive cold memory reclamation, similar problems existed. We we solved those by introducing dedicated static kernel modules such as DAMON_RECLAIM. Implement such static kernel module for access monitoring, namely DAMON_STAT. It monitors the entire physical address space with auto-tuned monitoring intervals. The auto-tuning is set to capture 4 % of observable access events in each snapshot while keeping the sampling intervals 5 milliseconds in minimum and 10 seconds in maximum. From a few production environments, we confirmed this setup provides high quality monitoring results with minimum overheads. The module therefore receives only one user input, whether to enable or disable it. It can be set on build or boot time via build configuration or kernel boot command line. It can also be overridden at runtime. Note that this commit only implements the DAMON control part of the module. Users could get the monitoring results via damon:damon_aggregated tracepoint, but that's of course not the recommended way. Following commits will implement convenient and optimized ways for serving the monitoring results to users. [sj@kernel.org: use IS_ENABLED() for enabled initial value] Link: https://lkml.kernel.org/r/20250604205619.18929-1-sj@kernel.org [sj@kernel.org: reset enabled when DAMON start failed] Link: https://lkml.kernel.org/r/20250706184750.36588-1-sj@kernel.org Link: https://lkml.kernel.org/r/20250604183127.13968-1-sj@kernel.org Link: https://lkml.kernel.org/r/20250604183127.13968-2-sj@kernel.org Signed-off-by: SeongJae Park Cc: Jonathan Corbet Signed-off-by: Andrew Morton

Revert "mm/damon/Kconfig: enable CONFIG_DAMON by default"

2025-06-10T17:22:15+00:00

This reverts commit 28615e6eed152f2fda5486680090b74aeed7b554. No, we don't make random features default to being on. Reported-by: Geert Uytterhoeven Cc: Andrew Morton Cc: SeongJae Park Signed-off-by: Linus Torvalds

mm/damon/Kconfig: enable CONFIG_DAMON by default

2025-06-01T05:46:12+00:00

As of this writing, multiple major distros including Alma, Amazon, Android, CentOS, Debian, Fedora, and Oracle are build-enabling DAMON (set CONFIG_DAMON[1]). Enabling it by default will save configuration setup time for the current and future DAMON users. Build-enabling DAMON does not introduce a real risk since it makes no behavioral change by default. It requires explicit user requests to do anything. Only one potential risk is making the size of the kernel a little bit larger. On a production-purpose configuration, it increases the resulting kernel package size by about 0.1 % of the final package file. I believe that's too small to be a real problem in common setups. Hence, the benefit of enabling CONFIG_DAMON outweighs the potential risk. Set CONFIG_DAMON by default. Link: https://oracle.github.io/kconfigs/?config=UTS_RELEASE&config=DAMON [1] Link: https://lkml.kernel.org/r/20250521042755.39653-3-sj@kernel.org Signed-off-by: SeongJae Park Acked-by: Honggyu Kim Signed-off-by: Andrew Morton

mm/damon/Kconfig: set DAMON_{VADDR,PADDR,SYSFS} default to DAMON

2025-06-01T05:46:11+00:00

Patch series "mm/damon: build-enable essential DAMON components by default". As of this writing, multiple major distros including Alma, Amazon, Android, CentOS, Debian, Fedora, and Oracle are build-enabling DAMON (set CONFIG_DAMON[1]). Configuring DAMON is not very easy, since it is disabled by default, and there are multiple essential options that need to be manually turned on, one by one. Make it easier, by grouping essential configurations to be enabled with one selection, and enabling build of the essential parts of DAMON by default. Note that build-enabling DAMON does not introduce any real risk, since it makes no behavioral change by default. It requires explicit user requests to do anything. Only one potential risk is making the size of the kernel a little bit larger. On a production-purpose configuration, it increases the resulting kernel package binary size by about 0.1 % of the final package file. I believe that's too small to be a real problem in common setups. DAMON_{VADDR,PADDR,SYSFS} are de-facto essential parts of DAMON for normal usages. Because those need to be enabled one by one, however, and there are other test-purpose or non-essential configurations, it is easy to be confused and make mistakes at setup. Make the essential configurations default to CONFIG_DAMON, so that those can be enabled by default with a single change. Link: https://oracle.github.io/kconfigs/?config=UTS_RELEASE&config=DAMON [1] Link: https://lkml.kernel.org/r/20250521042755.39653-1-sj@kernel.org Link: https://lkml.kernel.org/r/20250521042755.39653-2-sj@kernel.org Signed-off-by: SeongJae Park Acked-by: Honggyu Kim Signed-off-by: Andrew Morton

mm/damon: remove DAMON debugfs interface

2025-01-26T04:22:29+00:00

It's time to remove DAMON debugfs interface, which has deprecated long before in February 2023. Read the cover letter of this patch series for more details. All documents and related tests are also removed. Finally remove the interface. Link: https://lkml.kernel.org/r/20250106191941.107070-9-sj@kernel.org Signed-off-by: SeongJae Park Cc: Alex Shi Cc: Brendan Higgins Cc: David Gow Cc: Hu Haowen <2023002089@link.tyut.edu.cn> Cc: Jonathan Corbet Cc: Rae Moar Cc: Shuah Khan Cc: Yanteng Si Signed-off-by: Andrew Morton

mm/damon: remove DAMON debugfs interface kunit tests

2025-01-26T04:22:29+00:00

It's time to remove DAMON debugfs interface, which has deprecated long before in February 2023. Read the cover letter of this patch series for more details. Remove kunit tests for the interface, to prevent unnecessary test failures. Link: https://lkml.kernel.org/r/20250106191941.107070-8-sj@kernel.org Signed-off-by: SeongJae Park Cc: Alex Shi Cc: Brendan Higgins Cc: David Gow Cc: Hu Haowen <2023002089@link.tyut.edu.cn> Cc: Jonathan Corbet Cc: Rae Moar Cc: Shuah Khan Cc: Yanteng Si Signed-off-by: Andrew Morton

mm/damon/Kconfig: update DBGFS_KUNIT prompt copy for SYSFS_KUNIT

2024-11-07T22:38:08+00:00

CONFIG_DAMON_SYSFS_KUNIT_TEST prompt is copied from that for DAMON debugfs interface kunit tests, and not correctly updated. Fix it. Link: https://lkml.kernel.org/r/20241028233058.283381-6-sj@kernel.org Fixes: b8ee5575f763 ("mm/damon/sysfs-test: add a unit test for damon_sysfs_set_targets()") Signed-off-by: SeongJae Park Cc: Andrew Paniakin Cc: Brendan Higgins Cc: David Gow Cc: Shuah Khan Signed-off-by: Andrew Morton

mm/damon/Kconfig: update DAMON doc URL

2024-09-26T21:01:44+00:00

The old URL doesn't really work anymore and as the documentation has been integrated in the main kernel documentation site, change the URL to point to that. Link: https://lkml.kernel.org/r/20240924082331.11499-1-didi.debian@cknow.org Signed-off-by: Diederik de Haas Reviewed-by: SeongJae Park Signed-off-by: Andrew Morton

mm/damon: rename CONFIG_DAMON_DBGFS to DAMON_DBGFS_DEPRECATED

2024-02-22T18:24:45+00:00

DAMON debugfs interface is deprecated. The fact has documented by commit 5445fcbc4cda ("Docs/admin-guide/mm/damon/usage: add DAMON debugfs interface deprecation notice"). Commit 620932cd2852 ("mm/damon/dbgfs: print DAMON debugfs interface deprecation message") further started printing a warning message when users still use it. Many people don't read documentation or kernel log, though. Make the deprecation harder to be ignored using the approach of commit eb07c4f39c3e ("mm/slab: rename CONFIG_SLAB to CONFIG_SLAB_DEPRECATED"). 'make oldconfig' with 'CONFIG_DAMON_DBGFS=y' will get a new prompt with the explicit deprecation notice on the name. 'make olddefconfig' with 'CONFIG_DAMON_DBGFS=y' will result in not building DAMON debugfs interface. If there is a real user of DAMON debugfs interface, they will complain the change to the builder. Link: https://lkml.kernel.org/r/20240130013549.89538-3-sj@kernel.org Signed-off-by: SeongJae Park Cc: Alex Shi Cc: Hu Haowen <2023002089@link.tyut.edu.cn> Cc: Jonathan Corbet Cc: Shuah Khan Cc: Yanteng Si Signed-off-by: Andrew Morton