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Fri, 13 Mar 2026 04:09:58 -0700 (PDT) Received: from celestia.taila51cc2.ts.net ([2402:1980:89f2:c7ce:9a60:1bde:300a:8fcf]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-82a07340439sm5679444b3a.31.2026.03.13.04.09.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Mar 2026 04:09:57 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: damon@list.linux.dev, linux-mm@kvack.org Subject: [DAMON][Question] DAMON_STAT and DAMON_LRU_SORT module parameter conflict? Date: Fri, 13 Mar 2026 19:09:53 +0800 Message-ID: <20260313110953.37465-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 7AB764000D X-Stat-Signature: 39o4f6c6ekcfockdqq3tb1fkftigotm7 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1773400199-190730 X-HE-Meta: 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 tTWniULZ gdNKf8jn5uw6d5sQHtlrLbwDfA8cBGWD+XPZOaPSLWgszK7Xr4uRHVm+gAY6laQmbRFsDxsnJEkzrg3ZY6umCyOER7kQd7DHSbxyOfu4HSrilaB6dAplDcb2HflhjFxujM/aKGNKBLRmvSZWjiT7HSywOCA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: TL;DR ===== When CONFIG_DAMON_STAT_ENABLED_DEFAULT=y, enabling damon_lru_sort via sysfs "enabled" parameter returns -EBUSY. Is this expected behavior? If yes, should this limitation be documented? Reproduction ============ Environment: - Kernel: 7.0.0-rc3+ (x86_64) - VM: Virtme-ng (4G RAM, 2 CPUs) - Config: CONFIG_DAMON_STAT_ENABLED_DEFAULT=y, CONFIG_DAMON_LRU_SORT=y Steps: 1. cd /sys/module/damon_lru_sort/parameters 2. (optional) tune parameters: hot_thres_access_freq, cold_min_age, etc. 3. echo Y > enabled Result: bash: echo: write error: Device or resource busy Workaround: Disable CONFIG_DAMON_STAT_ENABLED_DEFAULT, or disable damon_stat at runtime before enabling damon_lru_sort. Questions ========= 1. Is this resource conflict between damon_stat and damon_lru_sort expected? 2. If yes, should this limitation be documented in: - Documentation/admin-guide/mm/damon/lru_sort.rst - Documentation/admin-guide/mm/damon/stat.rst Additional Context ================== - On major distros (Arch/Fedora), CONFIG_DAMON_STAT_ENABLED_DEFAULT is typically unset (disabled), so this issue may not affect most users. - However, for kernel developers or custom builds enabling both modules, clearer documentation or error handling would improve debuggability. Best regards, Liew Rui Yan