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timers: implement usleep_idle_range()

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Patch series "mm/damon: Fix fake /proc/loadavg reports", v3.

This patchset fixes DAMON's fake load report issue.  The first patch
makes yet another variant of usleep_range() for this fix, and the second
patch fixes the issue of DAMON by making it using the newly introduced
function.

This patch (of 2):

Some kernel threads such as DAMON could need to repeatedly sleep in
micro seconds level.  Because usleep_range() sleeps in uninterruptible
state, however, such threads would make /proc/loadavg reports fake load.

To help such cases, this commit implements a variant of usleep_range()
called usleep_idle_range().  It is same to usleep_range() but sets the
state of the current task as TASK_IDLE while sleeping.

Link: https://lkml.kernel.org/r/20211126145015.15862-1-sj@kernel.org
Link: https://lkml.kernel.org/r/20211126145015.15862-2-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: John Stultz <john.stultz@linaro.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
SeongJae Park 2021-12-10 14:46:22 -08:00 committed by Linus Torvalds
parent 0c941cf30b
commit e4779015fd
2 changed files with 22 additions and 8 deletions
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14
include/linux/delay.h
View file

@ -20,6 +20,7 @@
*/
#include <linux/math.h>
#include <linux/sched.h>
extern unsigned long loops_per_jiffy;
@ -58,7 +59,18 @@ void calibrate_delay(void);
void __attribute__((weak)) calibration_delay_done(void);
void msleep(unsigned int msecs);
unsigned long msleep_interruptible(unsigned int msecs);
void usleep_range(unsigned long min, unsigned long max);
void usleep_range_state(unsigned long min, unsigned long max,
unsigned int state);
static inline void usleep_range(unsigned long min, unsigned long max)
{
usleep_range_state(min, max, TASK_UNINTERRUPTIBLE);
}
static inline void usleep_idle_range(unsigned long min, unsigned long max)
{
usleep_range_state(min, max, TASK_IDLE);
}
static inline void ssleep(unsigned int seconds)
{

16
kernel/time/timer.c
View file

@ -2054,26 +2054,28 @@ unsigned long msleep_interruptible(unsigned int msecs)
EXPORT_SYMBOL(msleep_interruptible);
/**
* usleep_range - Sleep for an approximate time
* @min: Minimum time in usecs to sleep
* @max: Maximum time in usecs to sleep
* usleep_range_state - Sleep for an approximate time in a given state
* @min: Minimum time in usecs to sleep
* @max: Maximum time in usecs to sleep
* @state: State of the current task that will be while sleeping
*
* In non-atomic context where the exact wakeup time is flexible, use
* usleep_range() instead of udelay(). The sleep improves responsiveness
* usleep_range_state() instead of udelay(). The sleep improves responsiveness
* by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
* power usage by allowing hrtimers to take advantage of an already-
* scheduled interrupt instead of scheduling a new one just for this sleep.
*/
void __sched usleep_range(unsigned long min, unsigned long max)
void __sched usleep_range_state(unsigned long min, unsigned long max,
unsigned int state)
{
ktime_t exp = ktime_add_us(ktime_get(), min);
u64 delta = (u64)(max - min) * NSEC_PER_USEC;
for (;;) {
__set_current_state(TASK_UNINTERRUPTIBLE);
__set_current_state(state);
/* Do not return before the requested sleep time has elapsed */
if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
break;
}
}
EXPORT_SYMBOL(usleep_range);
EXPORT_SYMBOL(usleep_range_state);