From nobody Tue Jun 16 01:16:20 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 6D7703E929E; Tue, 14 Apr 2026 23:59:23 +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=1776211163; cv=none; b=WK6P4VMiGUEAQT5sPRLMZXR7WMCu6hF56Q+3k3/ROaFaTmNEbQq0YHh1i8kCoPIaCC6V9RkCrqR0PpDFJjY7vU1tRTAjcgHXSBI7IHSGhzrHIxmaXZ89Sja/I2RCMIQWEIP5jD7xcSLuiQcAJt7dcVxgH9WJJUWcDO3WJBdRsYU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776211163; c=relaxed/simple; bh=89KMBZu/gh+eCPCY4tm5mE3w5HQv3CWTICCzSSCwLjo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Rze0HJsXTAPorVHZoy6klTSqoa01kFxnP0InwYHQaEOaZQEWyM1s9HVrmo0Mo1Jkanil05CdS8GxbX/DnO7O6lZo0GLHpliNa7cagm2fZO73PedXiZfhvtwjwS4kikYd8b9fgjL6ZtpnsoP6JO/+zFDsYsq3hhWnQo1O4/cdZLA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BqCuFpEJ; 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="BqCuFpEJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 26A69C2BCB7; Tue, 14 Apr 2026 23:59:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776211163; bh=89KMBZu/gh+eCPCY4tm5mE3w5HQv3CWTICCzSSCwLjo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BqCuFpEJzlNl+RkLq7nmIRer8zwazZy31XdNlcdw+vRBT7cIO4caxhMKpQDa0UbqL OEeuuwNCrQWDr/JOjjCYlaXtmmdWmaGS0mbRxEXFEaffIRGcDzn+sbWqoO16D+69Bi RIvF/xcRqEhAAdH4AMtUUg4uiRlcqNCVbGHoUKeEaIkV8hA4UDaEhw7oyUX64k5xq3 DNpEqoNhW1ck7FhWhyPpYFG0z//8ilRNUGCclUJxUtkWCnoAw5Ut8WH/SMcIMi9CDS d0aBGkx+Ji4ZpOBmlQmbFcC3wkLGYDurs1xVhj6D1TSLgeQ17iCvsBh+NTC05xBCQ/ xhUB0Qf0LsvNg== From: SeongJae Park To: Cc: SeongJae Park , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [RFC PATCH v1.1 1/2] mm/damon/stat: add a parameter for reading kdamond pid Date: Tue, 14 Apr 2026 16:59:10 -0700 Message-ID: <20260414235912.98174-2-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260414235912.98174-1-sj@kernel.org> References: <20260414235912.98174-1-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 | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/mm/damon/stat.c b/mm/damon/stat.c index 99ba346f9e325..510c593a313b8 100644 --- a/mm/damon/stat.c +++ b/mm/damon/stat.c @@ -44,6 +44,15 @@ module_param(aggr_interval_us, ulong, 0400); MODULE_PARM_DESC(aggr_interval_us, "Current tuned aggregation interval in microseconds"); =20 +/* + * PID of the DAMON thread + * + * If DAMON_STAT is enabled, this becomes the PID of the worker thread. + * Else, -1. + */ +static int kdamond_pid __read_mostly =3D -1; +module_param(kdamond_pid, int, 0400); + static struct damon_ctx *damon_stat_context; =20 static unsigned long damon_stat_last_refresh_jiffies; @@ -260,6 +269,13 @@ static int damon_stat_start(void) damon_stat_context =3D NULL; return err; } + kdamond_pid =3D damon_kdamond_pid(damon_stat_context); + if (kdamond_pid < 0) { + err =3D kdamond_pid; + kdamond_pid =3D -1; + damon_destroy_ctx(damon_stat_context); + damon_stat_context =3D NULL; + return err; =20 damon_stat_last_refresh_jiffies =3D jiffies; call_control.data =3D damon_stat_context; @@ -269,6 +285,7 @@ static int damon_stat_start(void) static void damon_stat_stop(void) { damon_stop(&damon_stat_context, 1); + kdamond_pid =3D -1; damon_destroy_ctx(damon_stat_context); damon_stat_context =3D NULL; } --=20 2.47.3 From nobody Tue Jun 16 01:16:20 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 410253EC2F6; Tue, 14 Apr 2026 23:59:24 +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=1776211164; cv=none; b=UmVranEU4a1O+FZXuR+My2mppclmYKKDZlXEQr+t0QcCpujRuakJLG7ryi/DrnGD7mDbVPNTwE0uj3NwKZmKaJwprHGv75j8/X4sAvOx50s7PzIb2xhLhY3dgp98fFsYo5ObVnzu2yrhB+3qCZI5GCRmQAGqLp2gSxsj/jmEN90= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776211164; c=relaxed/simple; bh=Te4GL7YI2bga7ObPIqHKNdIOFUrcsNxgo3oTxgGUtEY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=OrySGSmFKnkbFaorHmYgtR1gHEap56wMnI0HTdv9jwc4IIcHjKcs8Z/U/c+jZsOYH4u/QENVD95R4/pziXEiFIWiJPLgTBeeNLAbfw8Wo6538E5c+M8kuzPvMi4+7knLzdXRgNPXnBsBlOWn739j7vnzLpy0HqvoNYj4yHroQ4o= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=H3R5nb/L; 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="H3R5nb/L" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74EFAC2BCB5; Tue, 14 Apr 2026 23:59:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776211164; bh=Te4GL7YI2bga7ObPIqHKNdIOFUrcsNxgo3oTxgGUtEY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=H3R5nb/LjForXo1hg9/adfUnX1uTLjvOLP3aU91OCaP/Ui0zSo99XMAuRsQVQRQoR W/TuwCOM27bvC3Q1PuQ7GFX1WOA7cJBn+1IsS7tSdyvIrQhxThdiZN1nQFdH97ooRZ 4EEC+sQOfAGCF+c29eYHfuf1zSwU8l2dAXxQa3tV+FPHjAa+7aMhcb/MGU2ZaFQV/K 5+aJ68VP8Mb2H1Fsu9WVbNwbiF4HTrCNNFhG7bQtAH4JpekEMVxCWDfOJPRQOjt7mP 3KWGZOIR2DFEOtuiAR1/7N9zHHkHSHdGPmV67kRFWM/wnLVVBotKY6HArgFfw/u5aT 4Zi1XGmk8ZnlQ== From: SeongJae Park To: Cc: SeongJae Park , "Liam R. Howlett" , Andrew Morton , 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: [RFC PATCH v1.1 2/2] Docs/admin-guide/mm/damon/stat: document kdamond_pid parameter Date: Tue, 14 Apr 2026 16:59:11 -0700 Message-ID: <20260414235912.98174-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260414235912.98174-1-sj@kernel.org> References: <20260414235912.98174-1-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