DAMON traces effective size quota from the second update, only if a change has been made by the update. Tracing only changed updates was an intentional decision to avoid unnecessary same value tracing. Always skipping the first value is just an unintended mistake. The mistake makes the tracepoint based investigation incomplete, because the first effective size quota is never traced. It is not a big issue when the 'consist' quota tuner is used, because it keeps changing the quota in the usual setup. However, when the 'temporal' tuner is used, the quota value is not changed before the goal achievement status is completely changed. For example, if the DAMOS scheme is started with an under-achieved goal, the quota is set to the maximum value, and kept the same value until the goal is achieved. Because DAMON skips the first value, the user cannot know what effective quota the current scheme is using. Only after the goal is achieved, the effective quota is changed to zero, and traced. Unconditionally trace the initial quota value to fix this problem. Note that the 'temporal' quota tuner was introduced by commit af738a6a00c1 ("mm/damon/core: introduce DAMOS_QUOTA_GOAL_TUNER_TEMPORAL"), which was added to 7.1-rc1. But even with the 'consist' quota tuner, the tracing is unintentionally incomplete. Hence this commit marks the introduction of the trace event as the broken commit. Fixes: a86d695193bf ("mm/damon: add trace event for effective size quota") Cc: # 6.17.x Signed-off-by: SeongJae Park --- Changes from RFC - RFC: https://lore.kernel.org/20260520005940.92003-1-sj@kernel.org - Drop RFC tag. mm/damon/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/damon/core.c b/mm/damon/core.c index 4e223857a0f99..0db6530825d1d 100644 --- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -2883,6 +2883,8 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s) if (!quota->total_charged_sz && !quota->charged_from) { quota->charged_from = jiffies; damos_set_effective_quota(c, s); + if (trace_damos_esz_enabled()) + damos_trace_esz(c, s, quota); } /* New charge window starts */ base-commit: 796dd9092b9c9d93dd48213582d45c43e93fa187 -- 2.47.3