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Fri, 13 Mar 2026 04:17:07 -0700 (PDT) Received: from celestia.taila51cc2.ts.net ([2402:1980:89f2:c7ce:9a60:1bde:300a:8fcf]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c73eb9966d9sm1678930a12.11.2026.03.13.04.17.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Mar 2026 04:17:07 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: damon@lists.linux.dev, linux-mm@kvack.org Subject: [Question] mm/damon: conflict between DAMON_STAT and DAMON_LRU_SORT? Date: Fri, 13 Mar 2026 19:17:02 +0800 Message-ID: <20260313111702.38667-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.53.0 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 0CD06C000A X-Stat-Signature: 39ucd3byqh1u6t633gdqzcoqwpuqdhig X-Rspam-User: X-HE-Tag: 1773400628-169870 X-HE-Meta: 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 2QAz97ZP 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 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