Each iteration of kdamond_fn() main loop caches and use the next aggregation time (next_aggregation_sis) because it can be updated in the middle, inside kdamond_call(). If that happens, damon_update_monitoring_result() is called for scaling the access frequency information of each region according to the changed intervals. The function does not update damon_region->last_nr_accesses when it is at the end of the aggregation, because it will anyway be reset after the function is executed, in kdamond_reset_aggregated(). Let's suppose damon_nr_accesses_mvsum() is called with the not yet updated last_nr_accesses. It will use the fresh next_aggregation_sis in the context instead of the cached one, unlike kdamond_fn(). As a result, use of not updated last_nr_acceses with the updated next_aggregation_sis result in returning wrong value. There is no such damon_nr_accesses_nvsum() call at the moment, so this is no problem. It is planned to add such calls, though. Prevent the issue by updating last_nr_accesses always. This adds overhead, but that's fine because the overhead is not big, and it is anyway not a fast path. Signed-off-by: SJ Park --- mm/damon/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/damon/core.c b/mm/damon/core.c index c588f943080f9..669b701e50a7d 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -877,6 +877,8 @@ static void damon_update_monitoring_result(struct damon_region *r, struct damon_attrs *old_attrs, struct damon_attrs *new_attrs, bool aggregating) { + r->last_nr_accesses = damon_nr_accesses_for_new_attrs( + r->last_nr_accesses, old_attrs, new_attrs); if (!aggregating) { r->nr_accesses = damon_nr_accesses_for_new_attrs( r->nr_accesses, old_attrs, new_attrs); @@ -888,8 +890,6 @@ static void damon_update_monitoring_result(struct damon_region *r, * interval. In other words, make the status like * kdamond_reset_aggregated() is called. */ - r->last_nr_accesses = damon_nr_accesses_for_new_attrs( - r->last_nr_accesses, old_attrs, new_attrs); r->nr_accesses_bp = r->last_nr_accesses * 10000; r->nr_accesses = 0; } -- 2.47.3