Changes from RFC (https://lore.kernel.org/damon/20230910034048.59191-1-sj@kernel.org/) - Add kselftest for damos_apply_interval_us sysfs file - Rebase on latest mm-unstable

DAMON-based operation schemes are applied for every aggregation interval. That is mainly because schemes are using nr_accesses, which be complete to be used for every aggregation interval.

This makes some DAMOS use cases be tricky. Quota setting under long aggregation interval is one such example. Suppose the aggregation interval is ten seconds, and there is a scheme having CPU quota 100ms per 1s. The scheme will actually uses 100ms per ten seconds, since it cannobe be applied before next aggregation interval. The feature is working as intended, but the results might not that intuitive for some users. This could be fixed by updating the quota to 1s per 10s. But, in the case, the CPU usage of DAMOS could look like spikes, and actually make a bad effect to other CPU-sensitive workloads.

Also, with such huge aggregation interval, users may want schemes to be applied more frequently.

DAMON provides nr_accesses_bp, which is updated for each sampling interval in a way that reasonable to be used. By using that instead of nr_accesses, DAMOS can have its own time interval and mitigate abovely mentioned issues.

This patchset makes DAMOS schemes to use nr_accesses_bp instead of nr_accesses, and have their own timing intervals. Also update DAMOS tried regions sysfs files and DAMOS before_apply tracepoint to use the new data as their source. Note that the interval is zero by default, and it is interpreted to use the aggregation interval instead. This avoids making user-visible behavioral changes.

Patches Seuqeunce -----------------

The first patch (patch 1/9) makes DAMOS uses nr_accesses_bp instead of nr_accesses, and following two patches (patches 2/9 and 3/9) updates DAMON sysfs interface for DAMOS tried regions and the DAMOS before_apply tracespoint to use nr_accesses_bp instead of nr_accesses, respectively.

The following two patches (patches 4/9 and 5/9) implements the scheme-specific apply interval for DAMON kernel API users and update the design document for the new feature.

Finally, the following four patches (patches 6/9, 7/9, 8/9 and 9/9) add support of the feature in DAMON sysfs interface, add a simple selftest test case, and document the new file on the usage and the ABI documents, repsectively.

SeongJae Park (9): mm/damon/core: make DAMOS uses nr_accesses_bp instead of nr_accesses mm/damon/sysfs-schemes: use nr_accesses_bp as the source of tried_regions/<N>/nr_accesses mm/damon/core: use nr_accesses_bp as a source of damos_before_apply tracepoint mm/damon/core: implement scheme-specific apply interval Docs/mm/damon/design: document DAMOS apply intervals mm/damon/sysfs-schemes: support DAMOS apply interval selftests/damon/sysfs: test DAMOS apply intervals Docs/admin-guide/mm/damon/usage: update for DAMOS apply intervals Docs/ABI/damon: update for DAMOS apply intervals

.../ABI/testing/sysfs-kernel-mm-damon | 7 ++ Documentation/admin-guide/mm/damon/usage.rst | 9 ++- Documentation/mm/damon/design.rst | 3 +- include/linux/damon.h | 17 +++- include/trace/events/damon.h | 2 +- mm/damon/core.c | 77 ++++++++++++++++--- mm/damon/dbgfs.c | 3 +- mm/damon/lru_sort.c | 2 + mm/damon/reclaim.c | 2 + mm/damon/sysfs-schemes.c | 40 ++++++++-- tools/testing/selftests/damon/sysfs.sh | 1 + 11 files changed, 141 insertions(+), 22 deletions(-)

base-commit: abf99d088da21843246382c7a95f21e886193c31