Re: [PATCH 2/2] mm/damon/tests/core-kunit: test PSI goal rounds under the temporal tuner

[KunWu Chan]

On Tue, Sep 15, 2026 at 2:09 PM Karl Mehltretter <kmehltretter@xxxxxxxxx> wrote:
>
> Exercise a PSI quota goal under the temporal tuner on its first
> round, its next measured round, and after a goal commit. Use
> ULONG_MAX as the target so the goal is not reached during the test.
> Then check that a measured round which does reach the target sets
> the quota to zero, and that the consist tuner keeps its quota over
> an unmeasured round.
>
> Without the previous patch, the first and the post-commit checks see
> a zero quota.
>
> Assisted-by: LLM
> Signed-off-by: Karl Mehltretter <kmehltretter@xxxxxxxxx>
> ---
>  mm/damon/tests/core-kunit.h | 69 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 69 insertions(+)
>
> diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
> index c01e6a75cadc..2b9b24ce7dad 100644
> --- a/mm/damon/tests/core-kunit.h
> +++ b/mm/damon/tests/core-kunit.h
> @@ -889,6 +889,74 @@ static void damos_test_commit_quota_goal(struct kunit *test)
>                         });
>  }
>
> +/*
> + * Unmeasured PSI goals must not disable the temporal quota.
> + * Keep sz * 10000 within a 32-bit unsigned long.
> + */
> +static void damos_test_set_effective_quota_temporal_psi(struct kunit *test)
> +{
> +       struct damon_ctx *c = damon_new_ctx();
> +       struct damos_access_pattern pattern = {};
> +       struct damos_quota quota = {
> +               .sz = SZ_64K,
> +               .goal_tuner = DAMOS_QUOTA_GOAL_TUNER_TEMPORAL,
> +       };
> +       struct damos_watermarks wmarks = {};
> +       struct damos_quota_goal src = {
> +               .metric = DAMOS_QUOTA_SOME_MEM_PSI_US,
> +               .target_value = ULONG_MAX,
> +       };
> +       struct damos_quota_goal *goal;
> +       struct damos *s;
> +
> +       if (!c)
> +               kunit_skip(test, "ctx alloc fail");
> +       s = damon_new_scheme(&pattern, DAMOS_STAT, 0, &quota, &wmarks,
> +                       NUMA_NO_NODE);
> +       if (!s) {
> +               damon_destroy_ctx(c);
> +               kunit_skip(test, "scheme alloc fail");
> +       }
> +       damon_add_scheme(c, s);
> +       goal = damos_new_quota_goal(DAMOS_QUOTA_SOME_MEM_PSI_US, ULONG_MAX);
> +       if (!goal) {
> +               damon_destroy_ctx(c);
> +               kunit_skip(test, "goal alloc fail");
> +       }
> +       damos_add_quota_goal(&s->quota, goal);
> +
> +       /* fresh goal, first tuning round */
> +       damos_set_effective_quota(c, s);
> +       KUNIT_EXPECT_EQ(test, s->quota.esz, (unsigned long)SZ_64K);
> +
> +       /* second round: last_psi_total is initialised now */

Could we also check goal->last_psi_total here?

The first tuning round should consume the U64_MAX sentinel
and establish the measured state.

Testing this explicitly would lock in that state transition.

Thanks,
Kunwu


> +       damos_set_effective_quota(c, s);
> +       KUNIT_EXPECT_EQ(test, s->quota.esz, (unsigned long)SZ_64K);
> +
> +       /* commit a PSI goal onto the initialised PSI goal */
> +       damos_commit_quota_goal(goal, &src);
> +       damos_set_effective_quota(c, s);
> +       KUNIT_EXPECT_EQ(test, s->quota.esz, (unsigned long)SZ_64K);
> +
> +       /* a measured round that reaches the target disables the quota */
> +       goal->target_value = 10;
> +       goal->last_psi_total = damos_get_some_mem_psi_total() - 10;
> +       /* U64_MAX marks an unmeasured goal, keep the sample away from it */
> +       if (goal->last_psi_total == U64_MAX)
> +               goal->last_psi_total--;
> +       damos_set_effective_quota(c, s);
> +       KUNIT_EXPECT_EQ(test, s->quota.esz, 0ul);
> +
> +       /* the consist tuner keeps its quota over an unmeasured round */
> +       s->quota.goal_tuner = DAMOS_QUOTA_GOAL_TUNER_CONSIST;
> +       s->quota.esz_bp = SZ_32K * 10000;
> +       damos_commit_quota_goal(goal, &src);
> +       damos_set_effective_quota(c, s);
> +       KUNIT_EXPECT_EQ(test, s->quota.esz, (unsigned long)SZ_32K);
> +
> +       damon_destroy_ctx(c);
> +}
> +
>  static void damos_test_commit_quota_goals_for(struct kunit *test,
>                 struct damos_quota_goal *dst_goals, int nr_dst_goals,
>                 struct damos_quota_goal *src_goals, int nr_src_goals)
> @@ -1887,6 +1955,7 @@ static struct kunit_case damon_test_cases[] = {
>         KUNIT_CASE(damos_test_new_filter),
>         KUNIT_CASE(damos_test_commit_quota_goal),
>         KUNIT_CASE(damos_test_commit_quota_goals),
> +       KUNIT_CASE(damos_test_set_effective_quota_temporal_psi),
>         KUNIT_CASE(damos_test_commit_quota),
>         KUNIT_CASE(damos_test_commit_dests),
>         KUNIT_CASE(damos_test_commit_filter),
> --
> 2.53.0
>