From nobody Tue Apr 14 14:05:39 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 745A62C08DC; Tue, 14 Apr 2026 04:50:13 +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=1776142213; cv=none; b=DAEWeIxg4h505r/v/pPiDLDypqrzk0s8ZAuBgM4SbpGnUhu65rC7ij+r10+V26T1/Icd0Dg/IxhxbjJ5p9hbbWWY4lmuEz/3UancOveGkXj/AHaFTVxfBMOxnB9+FJHXZjEyHssOGWq32HCQZQFh5OVxsFkRYUSfPkTkg4nwyKc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776142213; c=relaxed/simple; bh=tEc5S1Hg5SD+ndgy55KmKghFX44j7oOw2xQAGI0H8z8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=QVyKMFaFbaLg4TgGVwWuuwRHoB5lZftEYsX8Frov171nNNXMcFKWkRBMQ5dkthgkQvy+Yd9MqGvh29ptA8WvD8fl2wiWw6yPFcZt1ILZSST6fCvgKn9gkETOo9YmHqWRwywXNl6gbpKJfUC6Qbw6xEJNNU9InRyqMqsFdOUGI3c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ue0OyZPg; 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="Ue0OyZPg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20EB3C2BCB6; Tue, 14 Apr 2026 04:50:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776142213; bh=tEc5S1Hg5SD+ndgy55KmKghFX44j7oOw2xQAGI0H8z8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ue0OyZPgAKphMQmfgufZ2O980EarRHbBfjq+clKfoxTrPNS/sRMGwvKWPR+k2nI6V WbaeMSQbSvFgXYglf9GY0PmVsD4bDWriarNDgdciO4K8MMIn81q9svdQtQ3XwQMLBJ ezf7jCkUo1KLEVrxgWjTfPC+taBkQBnQ8ugAd+i05ppnCM3ejkHXCO7TsdB6nzlHwR sZyUAaF/35qC/gIDoOZVo+WvIQA1vsoUwirXaZDIbj1UVfxC9IxyVmxo3cHDT60tkP XRdUqjKLPIsfS16Hy1PlbGnp/ffQbaYoGITIJ9fcDaVMfHP0BM7q/MmLsffDjmvmBE Q7BlFiOVf8e3w== 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 1/2] mm/damon/stat: add a parameter for reading kdamond pid Date: Mon, 13 Apr 2026 21:49:59 -0700 Message-ID: <20260414045002.88110-2-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260414045002.88110-1-sj@kernel.org> References: <20260414045002.88110-1-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 | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/mm/damon/stat.c b/mm/damon/stat.c index 99ba346f9e325..21fa04d95eeac 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 +269,9 @@ 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) + return kdamond_pid; =20 damon_stat_last_refresh_jiffies =3D jiffies; call_control.data =3D damon_stat_context; @@ -269,6 +281,7 @@ 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 Apr 14 14:05:39 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 2E9332FD69A; Tue, 14 Apr 2026 04:50:14 +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=1776142214; cv=none; b=tcokSDjoeGnfzDIOluyQ+zjNKLHgLRahqWSsYcWo1y0bZ/0I3vIlkayhk7xwBvs3An7AZr/ZsIqm9fmQzVbILqyyHsRjl69UJz6YMJWQ+TrmS4RWAAn0PnbDHBpRjsB55ZbGYOSw1+4vHJNU0k0+A44WVRnFNZ64zPFfG4SQZn0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776142214; c=relaxed/simple; bh=Te4GL7YI2bga7ObPIqHKNdIOFUrcsNxgo3oTxgGUtEY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Og/DnKs2KLJ8+sbQEb4xNpK5fRvWOL2/LhO+Kzj8hR2gJZ39HGKMFvQtj+Kj12WP06MdbLdxpe/C5gI3dCZl53Loi8opR+pTsFIBw5qneyR8B1QOwFod3p9vXzLykX1KN5y98c7yc3QfSKP1xeLd7UR4vCOfhN1VfpRqHwNFSYc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=O41lfk3t; 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="O41lfk3t" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7B871C2BCB7; Tue, 14 Apr 2026 04:50:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776142214; bh=Te4GL7YI2bga7ObPIqHKNdIOFUrcsNxgo3oTxgGUtEY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=O41lfk3tx4LDd6ZI5YugjYAHTmDpBB3Z9WOtx/8ul230mVvea+IRclgfX9xOKMnuu yDmf15V5BDiXD1R+bZ77R7ARhB7U/vBqwGepCPGmxtqXpzWEjITNyg7ictoS3NQZdl MPISL4UKh2jZjC1YNFfj4btg1h7l3TTlTzyJOf3WowY8CxJLaEQe4ZCmWs/VymHLmz 4cc0A2K/rllsNntuRK333jXn0m774Txn6ntISewsHSPnX+rcUTaVdTH1PQswb8OOX5 2+Q9fb6uN1AMZ1PHvGJJXezj4OjYRrroNrfn58YXOmuOVv7a7is2F8eUQvzBUB4Q+p VeVw8Lc9xjSDw== 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 2/2] Docs/admin-guide/mm/damon/stat: document kdamond_pid parameter Date: Mon, 13 Apr 2026 21:50:00 -0700 Message-ID: <20260414045002.88110-3-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260414045002.88110-1-sj@kernel.org> References: <20260414045002.88110-1-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