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Thu, 24 Sep 2026 00:57:37 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: aethernet65535@gmail.com, akpm@linux-foundation.org, damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RESEND PATCH] mm/damon/tests/core-kunit: add test for unconditionally skipping the last region Date: Thu, 24 Sep 2026 15:57:42 +0800 Message-ID: <20260924075754.6839-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260919190953.86705-1-aethernet65535@gmail.com> References: <20260919190953.86705-1-aethernet65535@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 85F4580007 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: tk1yr431dro387bitotyyykyky87s9ef X-HE-Tag: 1790236659-22812 X-HE-Meta: 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 dy9PxalW uliz9S4rylrzQXuGEyUwvgL3JW8hXe3jmt0v9fKRuvZafjYIipNBFSYabBHXnQfFizw09V5ssMTHp3ZMoRedUr5Y4B/0C0ciKd1L4y3XRrPugfo54rvsPOcw1zDhr1R4gaSVnOWETVRyp2HYPErVFQ38E93d3JDu9rHyLXtNI1Q4xcd5cNtAQtvdpRSo0dU/8R9SrugSrqYMgsSqDqqGDDFMZu4FP8XJ74hP6TeU0uQGCA3cTzejYGm00CjpRFBZspr/2i7PUTqpssUKBWT/LsO2fL5GCo+HV8n4xUMTW72TLEGLTSHmFS5Lzj6ZkkDWC4mMBVwt30qYUJ1cC3FFE0PjF78J8WWIaGj1x3cc/o57TMfxXnmVcQBSNfOBzH9LaoRNQ0r32YtAXJS+2kiS4h31t6X/JP6yAD0OmC/ytqLognuhsuB5YpjIzBg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi SJ, Just a reminder, I think you might have missed the question I asked. On Sun, 20 Sep 2026 03:09:10 +0800 Liew Rui Yan wrote: > On Sat, 19 Sep 2026 09:07:25 -0700 SJ Park wrote: > > > On Sat, 19 Sep 2026 16:01:58 +0800 Liew Rui Yan wrote: > > > > > Commit 50585192bc2e ("mm/damon/schemes: skip already charged targets and > > > regions") introduced a minor issue that causes the last region to be > > > skipped before it is processed. > > > > > > Example: > > > > > > 1. Target has 2 regions: R1 (0-100 bytes) and R2 (100-200 bytes). > > > 2. Quota is configured to process only 100 bytes per window. > > > 3. Window 1: Processes R1 (0-100). Quota is full. charge_{target, > > > addr}_from is saved at (Target, 100). > > > 4. Window 2: The loop reaches R2. Because R2 is > > > damon_last_region(t), the old code unconditionally returns true, > > > skipping R2 entirely and resetting the charge_{target,addr}_from. > > > > > > Result: R2 is permanently skipped even though it has never been > > > processed. > > > > > > Add a test to prevent this regression in the future. > > > > > > Signed-off-by: Liew Rui Yan > > > > Other than a trivial style that I commented below, > > > > Reviewed-by: SJ Park > > > > [...] > > > +static void damon_test_last_region_quota_reset(struct kunit *test) > > > +{ > > [...] > > > + t = damon_new_target(); > > > + if (!t) { > > > + kunit_skip(test, "target alloc fail"); > > > + } > > > > Let's drop braces for single line, as suggested [1] in coding-style. > > I will change this in next revision. > > By the way, Sashiko reported an issue [1]: min_region_sz is not > power-of-2. While this do not cause any real issue in this test, > non-power-of-2's min_region_sz is not legal. Should min_region_sz > initial value set to power-of-2 value (e.g., PAGE_SIZE) in the next > revision? > [...] > [1] https://lore.kernel.org/damon/20260919081239.8A3D91F000FF@smtp.kernel.org [...] Best regards, Rui Yan