Commit fcf9a0ef authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Linus Torvalds

ksm: react on changing "sleep_millisecs" parameter faster

ksm thread unconditionally sleeps in ksm_scan_thread() after each
iteration:

	schedule_timeout_interruptible(
		msecs_to_jiffies(ksm_thread_sleep_millisecs))

The timeout is configured in /sys/kernel/mm/ksm/sleep_millisecs.

In case of user writes a big value by a mistake, and the thread enters
into schedule_timeout_interruptible(), it's not possible to cancel the
sleep by writing a new smaler value; the thread is just sleeping till
timeout expires.

The patch fixes the problem by waking the thread each time after the value
is updated.

This also may be useful for debug purposes; and also for userspace
daemons, which change sleep_millisecs value in dependence of system load.

Link: http://lkml.kernel.org/r/154454107680.3258.3558002210423531566.stgit@localhost.localdomainSigned-off-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: default avatarCyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e0975b2a
......@@ -296,6 +296,7 @@ static unsigned long ksm_run = KSM_RUN_STOP;
static void wait_while_offlining(void);
static DECLARE_WAIT_QUEUE_HEAD(ksm_thread_wait);
static DECLARE_WAIT_QUEUE_HEAD(ksm_iter_wait);
static DEFINE_MUTEX(ksm_thread_mutex);
static DEFINE_SPINLOCK(ksm_mmlist_lock);
......@@ -2388,6 +2389,8 @@ static int ksmd_should_run(void)
static int ksm_scan_thread(void *nothing)
{
unsigned int sleep_ms;
set_freezable();
set_user_nice(current, 5);
......@@ -2401,8 +2404,10 @@ static int ksm_scan_thread(void *nothing)
try_to_freeze();
if (ksmd_should_run()) {
schedule_timeout_interruptible(
msecs_to_jiffies(ksm_thread_sleep_millisecs));
sleep_ms = READ_ONCE(ksm_thread_sleep_millisecs);
wait_event_interruptible_timeout(ksm_iter_wait,
sleep_ms != READ_ONCE(ksm_thread_sleep_millisecs),
msecs_to_jiffies(sleep_ms));
} else {
wait_event_freezable(ksm_thread_wait,
ksmd_should_run() || kthread_should_stop());
......@@ -2821,6 +2826,7 @@ static ssize_t sleep_millisecs_store(struct kobject *kobj,
return -EINVAL;
ksm_thread_sleep_millisecs = msecs;
wake_up_interruptible(&ksm_iter_wait);
return count;
}
......
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