From nobody Sun Jun 14 06:04:04 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7355E1DC9B5; Sat, 2 May 2026 02:05:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777687515; cv=none; b=lJnb30g4UBvC3cM1F1tvuKEFtY2swlLAl2YjIl6CvQIh2kdDNkeS5t5JDe8ZJCvq7k56UNynyS1iq6og7ZnqHGtQe4zqvuetWWuJsmwa4mFNKCnZkqoadCtrLsYzfLQrTmV86rRF8GeumEU020O49sQqGzcuk//WoF3EaWce9AM= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777687515; c=relaxed/simple; bh=zmdkpdSWqP8doKAHn9uOBEj3q+JEz8NGiE/WXdGr6Wg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=B4kcu4eD71Mms2DLylq1DKBSc1Ry+ZIAGkj3qihybtTVXeb/BbzlJ5P3L4x6Ohl3/IGpAPN00+pkEB6X2luCaf0GErzDhr+8i3QT9Bm3Q9rbPNtIBYoveFVUQG1CRTULAEOOtSaveUSxlbGOmIqr20foUkVt2SRqmy+1yN2uaDQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ejtoxq0d; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ejtoxq0d" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 259E3C2BCC7; Sat, 2 May 2026 02:05:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777687515; bh=zmdkpdSWqP8doKAHn9uOBEj3q+JEz8NGiE/WXdGr6Wg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ejtoxq0dEbQHrdgOUI/B+UpvvG9khRixX7Cbk2C/wzsQtGIgcfY77JjchiMCcZ+JR Z5vBHkO+A/+OrB/QKrnR35mwCYVFC2rxPnU92Z8zruW46MF3l3kuHrdKgdJUQ1tzg6 BKHo5uh9hhkeQzLFy9ZDGY7C1XAdo1PV493MyhridiF/FMTqI2GaCiwM+hDkHvj1bQ +Nl6NHm8msrlLH2HK/VBUx6fWIdP2kt66YgpNPf4LPF8bwClnaDKuxsWththf23oVk kkdmz/abV5l5laXUpWuoxjRqGQWe2mHOwRL5jrtUBnprRcy43U92+bx39zGJ3DSn1J IAVtz4+6VTTfQ== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 1/2] mm/damon/stat: add a parameter for reading kdamond pid Date: Fri, 1 May 2026 19:05:03 -0700 Message-ID: <20260502020505.80822-2-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260502020505.80822-1-sj@kernel.org> References: <20260502020505.80822-1-sj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Knowing the pid of the kdamonds can help user-space management including monitoring of DAMON's system resource consumption. To make it easier, DAMON_SYSFS, DAMON_RECLAIM and DAMON_LRU_SORT provide the pid information. DAMON_STAT is not providing it, though. Expose the pid of DAMON_STAT kdamond via a new read-only module parameter, namely kdamond_pid. This also makes DAMON modules usage more standardized, because DAMON_RECLAIM and DAMON_LRU_SORT also provide the information via their read-only parameters of the same name. Signed-off-by: SeongJae Park --- mm/damon/stat.c | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) diff --git a/mm/damon/stat.c b/mm/damon/stat.c index f4d3203e92639..0e14f5bb8f75d 100644 --- a/mm/damon/stat.c +++ b/mm/damon/stat.c @@ -266,6 +266,45 @@ static int damon_stat_enabled_load(char *buffer, const= struct kernel_param *kp) return sprintf(buffer, "%c\n", damon_stat_enabled() ? 'Y' : 'N'); } =20 +static int damon_stat_kdamond_pid_store( + const char *val, const struct kernel_param *kp) +{ + /* + * kdamond_pid is read-only, but kernel command line could write it. + * Do nothing here. + */ + return 0; +} + +static int damon_stat_kdamond_pid_load( + char *buffer, const struct kernel_param *kp) +{ + int pid; + + if (!damon_stat_context) { + pid =3D -1; + } else { + pid =3D damon_kdamond_pid(damon_stat_context); + if (pid < 1) + pid =3D -1; + } + return sprintf(buffer, "%d\n", pid); +} + +static const struct kernel_param_ops kdamond_pid_param_ops =3D { + .set =3D damon_stat_kdamond_pid_store, + .get =3D damon_stat_kdamond_pid_load, +}; + +/* + * PID of the DAMON thread + * + * If DAMON_STAT is enabled, this becomes the PID of the worker thread. + * Else, -1. + */ +module_param_cb(kdamond_pid, &kdamond_pid_param_ops, NULL, 0400); +MODULE_PARM_DESC(kdamond_pid, "pid of the kdamond"); + static int __init damon_stat_init(void) { int err =3D 0; --=20 2.47.3 From nobody Sun Jun 14 06:04:04 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 510962C11E6; Sat, 2 May 2026 02:05:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777687516; cv=none; b=UFt3ana0XTiPKUDXgNF8ASO2tL5NNtGykcAzE71qF0cDPb5bVeip4fLxHpolRf8dH1FBXNzLkWu2j7RqarlMSXuXOXz2d/MQBikp5xWoIuOS59T25AcZV8EgBliOhsQhcYgLcITnf+EbPnHsZArwqTtZgn/v4Z7PtehQsQ14qA0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777687516; c=relaxed/simple; bh=Te4GL7YI2bga7ObPIqHKNdIOFUrcsNxgo3oTxgGUtEY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=NEWD4kwAdOmjcSvnaASmzCbzLIYQcp7ZhAM55Q3EwcmuzsEvITGslJ2D4Ht+V2+4prn5Pux6WC+7txTFpgrHMl1LScop+blfBEPy/0wJoxNdZoyPXc9u3dv3BMgdXXmQL2Afjq6HKC6d1ijMV6ZVU4EKfIrfKg8foN1g5bAzjnM= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ocaS+sPG; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ocaS+sPG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 80F73C2BCB7; Sat, 2 May 2026 02:05:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777687516; bh=Te4GL7YI2bga7ObPIqHKNdIOFUrcsNxgo3oTxgGUtEY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ocaS+sPGGQEFhUdiF2OuL4XrIeWnt97nZiMKzfHGwlTfxdNHUUxgxSQVBvdydiZSF vzEG9n1tPpOmN6kN2IRSXVqI4plFdE2BTZlMqM6jLkC5KAP2DFKBrqVljwHNo3FPfc JMzbzJDGmAlaCa7n5rRBMQhCVGLcawy3UhdROKE7Lzyn70w3ICvJ/1DkU6WbL13cRR x2GtazVbIiylT2gCtADUatDX+PPYA3hGBiamu43inIoAx2vPCRsNE+pChBV5JyGu/+ ML/M7iedM3lm9lXUJ7Alj357K2P0+nmURUN/8d4DVeL3ipckp9zxWFpD7DjujuK6go YcWCo1DZ3xe0Q== From: SeongJae Park To: Andrew Morton Cc: SeongJae Park , "Liam R. Howlett" , David Hildenbrand , Jonathan Corbet , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Shuah Khan , Suren Baghdasaryan , Vlastimil Babka , damon@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 2/2] Docs/admin-guide/mm/damon/stat: document kdamond_pid parameter Date: Fri, 1 May 2026 19:05:04 -0700 Message-ID: <20260502020505.80822-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260502020505.80822-1-sj@kernel.org> References: <20260502020505.80822-1-sj@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Update DAMON_STAT usage document for newly added kdamond_pid parameter. Signed-off-by: SeongJae Park --- Documentation/admin-guide/mm/damon/stat.rst | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/Documentation/admin-guide/mm/damon/stat.rst b/Documentation/ad= min-guide/mm/damon/stat.rst index c4b14daeb2dd6..46c5dd96aa2ed 100644 --- a/Documentation/admin-guide/mm/damon/stat.rst +++ b/Documentation/admin-guide/mm/damon/stat.rst @@ -89,3 +89,10 @@ percentiles of the idle time values via this read-only p= arameter. Reading the parameter returns 101 idle time values in milliseconds, separated by comma. Each value represents 0-th, 1st, 2nd, 3rd, ..., 99th and 100th percentile = idle times. + +kdamond_pid +----------- + +PID of the DAMON thread. + +If DAMON_STAT is enabled, this becomes the PID of the worker thread. Else= , -1. --=20 2.47.3