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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: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: DF1E840004 X-Rspam-User: X-Stat-Signature: oa4on3kmsfcf4dw7yh38ighptto3w6i9 X-HE-Tag: 1788926079-989819 X-HE-Meta: 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 qAVev+Ir 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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)