mm/damon/core: fix fake load reports due to uninterruptible sleeps

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/

Link: https://lkml.kernel.org/r/20211126145015.15862-3-sj@kernel.org
Fixes: 2224d8485492 ("mm: introduce Data Access MONitor (DAMON)")
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Signed-off-by: SeongJae Park <sj@kernel.org>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/damon/core.c b/mm/damon/core.c
index c381b3c..2daffd5 100644 (file)
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -981,9 +981,9 @@ 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 */
@@ -1038,7 +1038,7 @@ 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);