Aim-oriented DAMOS quota auto-tuning assumes the aggressiveness of the scheme (quota) and the quota goal metric are directly proportional. Depending on the scheme setup and usage, keeping the relationship can be challenging.
For example, let's suppose a memory tiering approach for higher upper tier utilization. One common idea for that (TPP) is utilizing two schemes, one for promotion and the other one for demotion. The promotion scheme migrates hot pages from lower tier to upper tier, aiming for high utilization of the upper tier. The demotion scheme migrates cold pages from upper tier to lower tier, aiming for head room free memory of the upper tier. Both schemes and their goals are in direct proportion. However, for this kind of use case, we need to implement two different goal metrics (per-node memory utilization and free memory ratio) while essentially the free memory ratio is just a complemented value of the utilization. To avoid adding too many new metrics, we are adding metrics that turn out to be really needed for each found use case. For example, some_mem_psi_us, node_eligible_mem_bp and hugepage_mem_bp don't have their complemented value version. But it is not really difficult to expect use cases that their complemented version can be useful. For example, hugepage_mem_bp use case may need a way to reduce the hugepage ratio. That would require a complemented version of hugepage_mem_bp. Adding a new metric for each of such use cases could make the number of metrics unnecessarily high, and discourage flexible usages of DAMOS. Add a new flag, quota goal complement, to allow flexible tuning goal setup without unnecessarily increasing the number of metrics. The flag specifies whether to use the complemented value of the given goal metric for the tuning. For example, if the complement flag is set, the upper tier memory utilization ratio metric works the same as the free memory ratio metric for the tier. Changes from RFC - RFC: https://lore.kernel.org/[email protected] - Avoid quota goal value underflow. - Fix usage doc for number of files in each goal directory. - Rebase to the latest mm-new. SJ Park (7): mm/damon/core: introduce damos_quota_goal->complement mm/damon: add complement argument to damos_new_quota_goal() mm/damon/sysfs-schemes: support quota goal complement flag mm/damon/tests/core-kunit: test quota_goal->complement commit Docs/mm/damon/design: document damos quota goal complement flag Docs/admin-guide/mm/damon/usage: update for quota goal complement file Docs/ABI/damon: update for quota goal metric complement sysfs file .../ABI/testing/sysfs-kernel-mm-damon | 6 ++++ Documentation/admin-guide/mm/damon/usage.rst | 15 +++++----- Documentation/mm/damon/design.rst | 13 +++++--- include/linux/damon.h | 4 ++- mm/damon/core.c | 25 ++++++++++++++-- mm/damon/lru_sort.c | 5 ++-- mm/damon/reclaim.c | 5 ++-- mm/damon/sysfs-schemes.c | 30 +++++++++++++++++++ mm/damon/tests/core-kunit.h | 4 ++- samples/damon/mtier.c | 2 +- 10 files changed, 88 insertions(+), 21 deletions(-) base-commit: 026f1215e57024b54116f6388ca96c64ff84f44d -- 2.47.3
