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Tue, 08 Sep 2026 20:54:37 -0700 (PDT) From: Kunwu Chan To: SJ Park Cc: Kunwu Chan , akpm@linux-foundation.org, lianux.mm@gmail.com, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/damon/tests/core-kunit: improve nr_samples_per_aggr test isolation Date: Wed, 9 Sep 2026 11:54:26 +0800 Message-ID: <20260909035430.2432886-1-kunwu.chan@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260908133651.96278-1-sj@kernel.org> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, 8 Sep 2026 06:36:50 -0700 SJ Park wrote: > Hi Kunwu, > > On Tue, 8 Sep 2026 14:36:35 +0800 Kunwu Chan wrote: > > > The damon_nr_samples_per_aggr() test sets both intervals to zero, > > which exercises two different fallback paths at once. > > > > Use separate compound initializers for each case so that each case > > tests one fallback path independently. Also make the overflow case > > use an explicit non-zero sample interval so that it does not depend > > on the zero sample interval fallback. > > Thank you for sharing this patch! > > > > > Signed-off-by: Kunwu Chan > > --- > > mm/damon/tests/core-kunit.h | 19 +++++++++++++++---- > > 1 file changed, 15 insertions(+), 4 deletions(-) > > > > diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h > > index c01e6a75cad..ff23208c181 100644 > > --- a/mm/damon/tests/core-kunit.h > > +++ b/mm/damon/tests/core-kunit.h > > @@ -627,12 +627,20 @@ static void damon_test_set_regions(struct kunit *test) > > > > static void damon_test_nr_samples_per_aggr(struct kunit *test) > > { > > - struct damon_attrs attrs = { > > + struct damon_attrs attrs; > > + > > + /* Zero sample interval is treated as one. */ > > + attrs = (struct damon_attrs){ > > .sample_interval = 0, > > - .aggr_interval = 0, > > + .aggr_interval = 5000, > > }; > > + KUNIT_EXPECT_EQ(test, damon_nr_samples_per_aggr(&attrs), 5000); > > Thank you for adding this test case. > > > > > - /* Zero aggregation interval doesn't cause division by zero */ > > + /* Zero samples per aggregation is treated as one. */ > > + attrs = (struct damon_attrs){ > > + .sample_interval = 5000, > > + .aggr_interval = 0, > > + }; > > KUNIT_EXPECT_EQ(test, damon_nr_samples_per_aggr(&attrs), 1); > > But damon_set_attrs() disallows sample intervals that are larger than the > aggregation intervals. Hence this setup is somewhat unrealistic. Should we > set sample_interval zero? Good point. I checked damon_set_attrs() as well, and the `sample_interval <= aggr_interval` constraint makes `0/0` the consistent boundary case here. I'll update the second case accordingly. Thanks, KunWu > > > > > /* > > @@ -640,7 +648,10 @@ static void damon_test_nr_samples_per_aggr(struct kunit *test) > > * overflow > > */ > > if (ULONG_MAX > UINT_MAX) { > > - attrs.aggr_interval = (unsigned long)UINT_MAX + 1; > > + attrs = (struct damon_attrs){ > > + .sample_interval = 1, > > + .aggr_interval = (unsigned long)UINT_MAX + 1, > > + }; > > KUNIT_EXPECT_EQ(test, damon_nr_samples_per_aggr(&attrs), > > UINT_MAX); > > } > > > > base-commit: d118502628f8b673be9023db8bdf878f64a7ed45 > > -- > > 2.43.0 > > > Thanks, > SJ > Sent using hkml (https://github.com/sjp38/hackermail)