On Wed, 24 Nov 2021 14:52:19 +0000 SeongJae Park sj@kernel.org wrote:
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.
--- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -12,6 +12,8 @@ #include <linux/kthread.h> #include <linux/mm.h> #include <linux/random.h> +#include <linux/sched.h> +#include <linux/sched/debug.h> #include <linux/slab.h> #include <linux/string.h> @@ -976,12 +978,25 @@ static unsigned long damos_wmark_wait_us(struct damos *scheme) return 0; } +/* sleep for @usecs in idle mode */ +static void __sched damon_usleep_idle(unsigned long usecs) +{
- ktime_t exp = ktime_add_us(ktime_get(), usecs);
- u64 delta = usecs * NSEC_PER_USEC / 100; /* allow 1% error */
- for (;;) {
__set_current_state(TASK_IDLE);if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))break;- }
+}
Let's not copy-n-paste usleep_range() into damon code?
A new usleep_idle_range() in kernel/time/timer.c seems like a worthwhile addition. Perhaps usleep_idle_range() and usleep_range() can be static inline wrappers against a new, more general function in kernel/time/timer.c - usleep_range_state(min, max, state)?