On Wed, 24 Nov 2021 14:52:19 +0000 SeongJae Park <sj@xxxxxxxxxx> 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)?
