[PATCH v3 0/2] mm/damon/core: Performance optimizations for the kdamond hot path

Josh Law
2026-03-22T21:43:29Z

Hello,

This patch series provides two performance optimizations for the DAMON
core, specifically targeting the hot paths in kdamond.

The first patch optimizes kdamond_apply_schemes() by inverting the loop
order. By iterating over schemes first and regions second, we can
evaluate scheme-level invariants (like activation status and quotas)
once per scheme rather than for every single region. This significantly
reduces CPU overhead when multiple schemes are present or when quotas
are reached.

The second patch eliminates a hardware integer division in
damon_max_nr_accesses() by using the pre-cached aggr_samples value.
Since this function is called once per region per sampling interval,
removing the division provides a measurable reduction in CPU cycles
spent in the access rate update path.

Changes from v2:
- Fix multi-line if statement alignment in the first patch to satisfy
checkpatch --strict.

Changes from v1:
- Use min_t(unsigned long, ...) in damon_max_nr_accesses() to satisfy
checkpatch warnings and improve readability.

Josh Law (2):
mm/damon/core: optimize kdamond_apply_schemes() by inverting scheme
and region loops
mm/damon/core: eliminate hot-path integer division in
damon_max_nr_accesses()

include/linux/damon.h | 3 +-
mm/damon/core.c | 68 ++++++++++++++++++-------------------------
2 files changed, 29 insertions(+), 42 deletions(-)

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2.43.0