DAMON provides damon_callback API that notifies monitoring events and allows safe access to damon_ctx internal data. Users can set and unset callback functions for different monitoring events in damon_ctx. Then DAMON worker thread (kdamond) calls back the functions on the events as long as the function is set on the damon_ctx. It is designed in such simple way because it was sufficient for usages of DAMON at the early days. We also wanted to make it flexible so that API client code can implement any required additional features on top of damon_callback on their demands. As expected, more sophisticated usages have invented. Online updates of parameters or DAMOS auto-tuning inputs and retrieval of DAMOS statistics and tried regions are notable such usages. Because damon_callback doesn't provide any explict synchronization mechanism, the user ABIs for exposing such functionalities are implemented in asynchronous ways (DAMON_RECLAIM and DAMON_LRU_SORT}), or synchronous ways (DAMON_SYSFS) with additional synchronization mechanisms that built inside the ABI implementation, on top of damon_callback. So damon_callback is working as expected. However, the additional mechanisms built inside ABI on top of damon_callback beocming somewhat too big and not easy to maintain. damon_callback is basically simple enougy to use in not only correct but also wrong ways. The additional mechanisms can be easier to maintain when implemented inside core logic. Introduce two new DAMON core API, namely 'damon_call()' and 'damos_walk()'. The two functions support synchronous access to - damon_ctx internal data including DAMON parameters and monitoring results, and - DAMOS-specific data such as regions that each DAMOS action is applied, respectively. And replace most of damon_callback usages from DAMON sysfs with the new core API functions. Online DAMON parameters tuning feature is not replaced in this series, since it has specific callback timing assumptions that require more works. Patch sequence ============== First two patches removes unnecessary synchronization dependency of clear_schemes_tried_regions command handling. Third patch implements one of the new DAMON API, damon_call(). Three patches replacing damon_callback usages in DAMON sysfs interface using damon_call() follow. Then, seventh patch introduces the other new DAMON API, damos_walk(). Eighth patch replaces two damon_callback usages in DAMON sysfs interface using damos_walk(). The ninth patch finally cleans up code that no more being used. SeongJae Park (9): mm/damon/sysfs-schemes: remove unnecessary schemes existence check in damon_sysfs_schemes_clear_regions() mm/damon/sysfs: handle clear_schemes_tried_regions from DAMON sysfs context mm/damon/core: implement damon_call() mm/damon/sysfs: use damon_call() for update_schemes_stats mm/damon/sysfs: use damon_call() for commit_schemes_quota_goals mm/damon/sysfs: use damon_call() for update_schemes_effective_quotas mm/damon/core: implement damos_walk() mm/damon/sysfs: use damos_walk() for update_schemes_tried_{bytes,regions} mm/damon/sysfs: remove unused code for schemes tried regions update include/linux/damon.h | 59 ++++++++++- mm/damon/core.c | 220 +++++++++++++++++++++++++++++++++++++++ mm/damon/sysfs-common.h | 16 +-- mm/damon/sysfs-schemes.c | 206 ++++-------------------------------- mm/damon/sysfs.c | 187 +++++++++++++++------------------ 5 files changed, 386 insertions(+), 302 deletions(-) base-commit: e5c48d400cab89a0539ce822ba805f0ad4209e87 -- 2.39.5