DAMOS fitlers are exclusive filters. It only excludes memory of given criterias from the DAMOS action targets. This has below limitations. First, the name is not explicitly explaining the behavior. This actually resulted in users' confusions[1]. Secondly, combined uses of multiple filters provide restriced coverages. For example, building a DAMOS scheme that applies the action to memory that belongs to cgroup A "or" cgroup B is impossible. A workaround would be using two schemes that fitlers out memory that not belong to cgroup A and cgroup B, respectively. It is cumbersome, and difficult to control quota-like per-scheme features in orchastration. Monitoring of filter-passed memory statistic will also be complicated. Extend DAMOS filters to support not only exclusion (blocking), but also inclusion (pass-through) behavior. For this, add a new damos_filter struct field called 'pass' for DAMON kernel API users. The filter works as an inclusion filter or an exclusion filter when it is set or unset, respectively. For DAMON user-space ABI users, add a DAMON sysfs file of same name under DAMOS filter sysfs directory. To prevent exposing a behavioral change to old users, set the blocking as the default behavior. Note that pass filters work for only inclusion, not exclusion of memory that not satisfying the criteria. And the default behavior of DAMOS for memory that no filter has involved is that the action can be applied to those. This means that installing pass filters without block filters after them is not useful for some usecases. Read the design document update part of this patch series for more details. [1] https://lore.kernel.org/20240320165619.71478-1-sj@xxxxxxxxxx Changes from RFC v2 (https://lore.kernel.org/20241227210819.63776-1-sj@xxxxxxxxxx) - Wordsmith messages - Wordsmith design documentation about monitoring-purpose usage - Rebase on latest mm-unstable Changes from RFC v1 (https://lore.kernel.org/20241226221445.78433-1-sj@xxxxxxxxxx) - Fix encoding issue on the last patch SeongJae Park (10): mm/damon: fixup damos_filter kernel-doc mm/damon/core: add damos_filter->pass field mm/damon/core: support damos_filter->pass mm/damon/paddr: support damos_filter->pass mm/damon: add pass argument to damos_new_filter() mm/damon/sysfs-schemes: add a file for setting damos_filter->pass Docs/mm/damon/design: document pass/block filters behaviors Docs/ABI/damon: document DAMOS filter pass sysfs file Docs/admin-guide/mm/damon/usage: omit DAMOS filter details in favor of design doc Docs/admin-guide/mm/damon/usage: document DAMOS filter 'pass' sysfs file .../ABI/testing/sysfs-kernel-mm-damon | 14 +++-- Documentation/admin-guide/mm/damon/usage.rst | 55 ++++++++++--------- Documentation/mm/damon/design.rst | 34 ++++++++++-- include/linux/damon.h | 15 +++-- mm/damon/core.c | 12 ++-- mm/damon/paddr.c | 9 +-- mm/damon/reclaim.c | 2 +- mm/damon/sysfs-schemes.c | 32 ++++++++++- mm/damon/tests/core-kunit.h | 14 ++--- 9 files changed, 130 insertions(+), 57 deletions(-) -- 2.39.5
