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bh=9nWd2JiHbGpFxdKtIgR1/mA2jBP+r1D6KF4ucSMyulY=; b=p9sn7SP2ztHNii/Np0IzUgnjn26MoK88tkMnckxJldO1qMOqAtMSyDiQpaPtgM2Kn2E4nC OD+pPwxnGtkmd8BMsYqtoqgTcL1AuYZlgI/IOzU7NnNXpn5pLOs/uc4wtlvTShGaxWR0BC 5Wg8xrh39lLX2FjuqPVRzBLwhBmHDFg= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=dtbX8mVL; spf=pass (imf22.hostedemail.com: domain of sj@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 5995E601FA; Fri, 28 Aug 2026 01:47:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE1101F00AC4; Fri, 28 Aug 2026 01:47:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787881629; bh=9nWd2JiHbGpFxdKtIgR1/mA2jBP+r1D6KF4ucSMyulY=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=dtbX8mVLoREWGaHmBM5m9kXliDsh2AQfn0hrzWT7rWHB/eaufkaZ43YdaBE5485NG qMUCaHb0VIsQUV5/EfZdhs25mD+BsRV0UyBoYHNBAyzu0KrQkWdogw8wF/puukDrDd BT3HFeCdQ97JhybLUtgPXRR55Jrav7TuPg7gGKmxukLTLgA321GvoZQRVNPmoXJfqc g89xd3XGWdfQvhoOp7ENaxFZDliNMY2sqMSNtgZMozkfskvuRXe83gB2jeQyFPLLyR 5LrwkykKG96zwmt1q3iBUqlPekmRTXzAhNkjdKNnDlUJa5iUPIf0I0c1SS2qvnv6/O 79c9OP49m95zA== From: SJ Park To: Cc: SJ Park , stable@vger.kernel.org, Andrew Morton , Quanmin Yan , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1.2 4/4] mm/damon/sysfs: set next refresh jiffies per sysfs context Date: Thu, 27 Aug 2026 18:46:58 -0700 Message-ID: <20260828014659.121058-5-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260828014659.121058-1-sj@kernel.org> References: <20260828014659.121058-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: DC94EC0009 X-Stat-Signature: qb13da5tshpmwhfc1d8wzwnd6w181rm3 X-HE-Tag: 1787881629-393331 X-HE-Meta: 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 M6x99bnc mWy+3vA9jI7+wKt2yxw6xb2JjVwM29BTU7bCnHp+nOPcDntiZkHT9IVto6Ocgl9iNzGBUW6jNRbej/2SK6GtEqA3aqkd4bunz5WuIr0MdsZCjul8xhdrlVwiwX4ryjRxBRmBN+o+Q1Uk7zYImmZciZpUBHPMCPZtTq99G/Ht33I9Qd25YfxChJpCW7IGvTTs9nofRT+d8wWZ0+Np+JKWrG0aHrHGwra+XlhYNBNl650PXt+A= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When 'refresh_ms' is set, DAMON sysfs interface periodically updates auto-tuned parameters and DAMOS stats. The timestamp for the next refresh is initialized when a DAMON context starts, and updated in its damon_call() callback function. That is, each DAMON context updates it. However, the timestamp is a global variable that is shared with all the contexts. When there are multiple DAMON contexts having different refresh_ms, the update frequency will be changed, depending on the order of the contexts. When there are multiple kdamonds, it will be even more chaotic. Fix the problem by having the timestamp per each context. The user impact is not very critical. It does not leak, corrupt or crash. The update will not be faster or slower than the lowest and largest refresh_ms values of the contexts, respectively. The user can also manually ask the updates on demand using kdamond state commands. That said, clearly this is a bug and can easily be reproduced. Fixes: 9fd7bb5083d1 ("mm/damon/sysfs: change next_update_jiffies to a global variable") Cc: # 6.18.x Signed-off-by: SJ Park --- mm/damon/sysfs.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c index e3858ffab4b22..f05b256c90ee7 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1789,6 +1789,7 @@ struct damon_sysfs_kdamond { struct damon_sysfs_contexts *contexts; struct damon_ctx *damon_ctx; unsigned int refresh_ms; + unsigned long next_refresh_jiffies; }; static struct damon_sysfs_kdamond *damon_sysfs_kdamond_alloc(void) @@ -2215,17 +2216,15 @@ static struct damon_ctx *damon_sysfs_build_ctx( return ctx; } -static unsigned long damon_sysfs_next_update_jiffies; - static int damon_sysfs_repeat_call_fn(void *data) { struct damon_sysfs_kdamond *sysfs_kdamond = data; if (!sysfs_kdamond->refresh_ms) return 0; - if (time_before(jiffies, damon_sysfs_next_update_jiffies)) + if (time_before(jiffies, sysfs_kdamond->next_refresh_jiffies)) return 0; - damon_sysfs_next_update_jiffies = jiffies + + sysfs_kdamond->next_refresh_jiffies = jiffies + msecs_to_jiffies(sysfs_kdamond->refresh_ms); if (!mutex_trylock(&damon_sysfs_lock)) @@ -2273,8 +2272,8 @@ static int damon_sysfs_turn_damon_on(struct damon_sysfs_kdamond *kdamond) } kdamond->damon_ctx = ctx; - damon_sysfs_next_update_jiffies = - jiffies + msecs_to_jiffies(kdamond->refresh_ms); + kdamond->next_refresh_jiffies = jiffies + + msecs_to_jiffies(kdamond->refresh_ms); repeat_call_control->fn = damon_sysfs_repeat_call_fn; repeat_call_control->data = kdamond; -- 2.47.3