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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> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 2DA6EC0002 X-Stat-Signature: mk6q4sgiwmkahm3rdt81f6ekxw8adr9h X-Rspam-User: X-HE-Tag: 1776142214-250945 X-HE-Meta: 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 5iN2mBM0 CRKeM86Q2nUJIdp7OBHwIbaKlon6RRhQDdewHIDpbZiA51wIate/637KBnawZTMeE6yGxOYKykFn0tvKQp/NjbXO8qe59f2y7PIVP8ZCQn00Nm8KNXkJYZWdd4uHFgx3oqFZg0Upxp1qMISnXdas4sJxJ7z6wqdAw/LAlM+rjcEefLY1rWkZC6sVkBiFMYlxJyaqH1vYRPikdj7X/QIz7tk7t/xECClc9dZoV Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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"); +/* + * 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 = -1; +module_param(kdamond_pid, int, 0400); + static struct damon_ctx *damon_stat_context; static unsigned long damon_stat_last_refresh_jiffies; @@ -260,6 +269,9 @@ static int damon_stat_start(void) damon_stat_context = NULL; return err; } + kdamond_pid = damon_kdamond_pid(damon_stat_context); + if (kdamond_pid < 0) + return kdamond_pid; damon_stat_last_refresh_jiffies = jiffies; call_control.data = 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 = -1; damon_destroy_ctx(damon_stat_context); damon_stat_context = NULL; } -- 2.47.3