From fcf9a0ef8dc3a3fb8be9de12b0e006c85ed5dc29 Mon Sep 17 00:00:00 2001 From: Kirill Tkhai Date: Fri, 28 Dec 2018 00:38:40 -0800 Subject: 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.localdomain Signed-off-by: Kirill Tkhai Acked-by: Cyrill Gorcunov Reviewed-by: Andrew Morton Cc: Michal Hocko Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/ksm.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) (limited to 'mm/ksm.c') diff --git a/mm/ksm.c b/mm/ksm.c index 38c0360482fa..6c48ad13b4c9 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -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; } -- cgit v1.2.3-59-g8ed1b