From:   SeongJae Park <sj@kernel.org>
To:     akpm@linux-foundation.org
Cc:     john.stultz@linaro.org, tglx@linutronix.de, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, SeongJae Park <sj@kernel.org>,
        stable@vger.kernel.org
Subject: [PATCH v2 2/2] mm/damon/core: Fix fake load reports due to uninterruptible sleeps
Date:   Thu, 25 Nov 2021 16:08:30 +0000
Message-Id: <20211125160830.30153-3-sj@kernel.org>
In-Reply-To: <20211125160830.30153-1-sj@kernel.org>
References: <20211125160830.30153-1-sj@kernel.org>
Precedence: bulk

Because DAMON sleeps in uninterruptible mode, /proc/loadavg reports fake
load while DAMON is turned on, though it is doing nothing.  This can
confuse users[1].  To avoid the case, this commit makes DAMON sleeps in
idle mode.

[1] https://lore.kernel.org/all/11868371.O9o76ZdvQC@natalenko.name/

Fixes: 2224d8485492 ("mm: introduce Data Access MONitor (DAMON)")
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org> # 5.15.x
---
 mm/damon/core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/damon/core.c b/mm/damon/core.c
index daacd9536c7c..8cd8fddc931e 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -979,9 +979,9 @@ static unsigned long damos_wmark_wait_us(struct damos *scheme)
 static void kdamond_usleep(unsigned long usecs)
 {
 	if (usecs > 100 * 1000)
-		schedule_timeout_interruptible(usecs_to_jiffies(usecs));
+		schedule_timeout_idle(usecs_to_jiffies(usecs));
 	else
-		usleep_range(usecs, usecs + 1);
+		usleep_idle_range(usecs, usecs + 1);
 }
 
 /* Returns negative error code if it's not activated but should return */
@@ -1036,7 +1036,7 @@ static int kdamond_fn(void *data)
 				ctx->callback.after_sampling(ctx))
 			done = true;
 
-		usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
+		kdamond_usleep(ctx->sample_interval);
 
 		if (ctx->primitive.check_accesses)
 			max_nr_accesses = ctx->primitive.check_accesses(ctx);
-- 
2.17.1