From: SeongJae Park sj@kernel.org Subject: 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 ---

mm/damon/core.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/mm/damon/core.c~mm-damon-core-fix-fake-load-reports-due-to-uninterruptible-sleeps +++ a/mm/damon/core.c @@ -981,9 +981,9 @@ static unsigned long damos_wmark_wait_us 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); _