From: SeongJae Park sj@kernel.org
commit 70e9274805fccfd175d0431a947bfd11ee7df40e upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/damon/core.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
--- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -357,6 +357,15 @@ int damon_start(struct damon_ctx **ctxs, return err; }
+static void kdamond_usleep(unsigned long usecs) +{ + /* See Documentation/timers/timers-howto.rst for the thresholds */ + if (usecs > 20 * 1000) + schedule_timeout_idle(usecs_to_jiffies(usecs)); + else + usleep_idle_range(usecs, usecs + 1); +} + /* * __damon_stop() - Stops monitoring of given context. * @ctx: monitoring context @@ -370,8 +379,7 @@ static int __damon_stop(struct damon_ctx ctx->kdamond_stop = true; mutex_unlock(&ctx->kdamond_lock); while (damon_kdamond_running(ctx)) - usleep_range(ctx->sample_interval, - ctx->sample_interval * 2); + kdamond_usleep(ctx->sample_interval); return 0; } mutex_unlock(&ctx->kdamond_lock); @@ -670,7 +678,7 @@ static int kdamond_fn(void *data) ctx->callback.after_sampling(ctx)) set_kdamond_stop(ctx);
- 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);