[PATCH v3 2/2] mm/damon/core: Fix fake load reports due to uninterruptible sleeps

From: SeongJae Park
Date: Fri Nov 26 2021 - 09:52:29 EST


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@xxxxxxxxxxxxxx/

Fixes: 2224d8485492 ("mm: introduce Data Access MONitor (DAMON)")
Reported-by: Oleksandr Natalenko <oleksandr@xxxxxxxxxxxxxx>
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 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