DAMON resets the age of a region if its nr_accesses value has significantly changed. Specifically, the threshold is calculated as 20% of largest nr_accesses of the current snapshot. This means that regions changing the nr_accesses from zero to small non-zero value or from a small non-zero value to zero will keep the age. Since many users treat zero nr_accesses regions special, this can be confusing. Kernel code including DAMOS' regions priority calculation and DAMON_STAT's idle time calculation also treat zero nr_accesses regions special. Make it unconfusing by resetting the age when the nr_accesses changes between zero and a non-zero value. Signed-off-by: SeongJae Park Reviewed-by: Joshua Hahn --- mm/damon/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index be5942435d78..ff2c6bb30621 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2261,6 +2261,8 @@ static void damon_merge_regions_of(struct damon_target *t, unsigned int thres, damon_for_each_region_safe(r, next, t) { if (abs(r->nr_accesses - r->last_nr_accesses) > thres) r->age = 0; + else if ((r->nr_accesses == 0) != (r->last_nr_accesses == 0)) + r->age = 0; else r->age++; -- 2.39.5