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Sat, 19 Sep 2026 19:37:35 -0700 (PDT) From: Donggeun Yoo To: SJ Park Cc: Donggeun Yoo , akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v1 1/2] mm/damon/core: prevent size quota overflow in the temporal goal tuner Date: Sun, 20 Sep 2026 11:37:28 +0900 Message-ID: <20260920023730.2468388-1-donggeunyoo.kernel@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260919165509.86678-1-sj@kernel.org> References: <20260919071324.1583280-2-donggeunyoo.kernel@gmail.com> <20260919165509.86678-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E772540002 X-Stat-Signature: 71xbhsypbxcjdhehe994s1admn4ymwre X-Rspam-User: X-HE-Tag: 1789871858-251914 X-HE-Meta: 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 HQkoTX1j 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi SJ, Thank you for the review, and for pointing me at addr_unit -- I did not know about it. On Sat, 19 Sep 2026 09:55:08 -0700 SJ Park wrote: > For 32-bit machines, we have addr_unit parameter. I believe use of it could > effectively solve this kind of issues. Correct me if I'm wrong. You are right that it helps, and quite a lot: with a larger unit the same amount of memory is written to quotas/bytes as a smaller number, so the boundary is much harder to reach in practice. It does not move the boundary itself, though, since the multiply is on the value written whatever the unit means. And as you say, only paddr implements addr_unit, so vaddr and fvaddr get nothing from it. The 64-bit case turned out to be a little more than theoretical too. bytes_store() takes whatever kstrtoul() parses, so a quotas/bytes above 1844674407370955 wraps there with no scaling involved. v2 says both in the changelog, and your suggestion about the user documents became a third patch. I also took your form of the guard; it is a one-line diff and it reads better. https://lore.kernel.org/damon/20260920023111.2466265-1-donggeunyoo.kernel@gmail.com/ Thanks, Donggeun