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authorKirill Tkhai <ktkhai@virtuozzo.com>2018-12-28 00:38:40 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-28 12:11:51 -0800
commitfcf9a0ef8dc3a3fb8be9de12b0e006c85ed5dc29 (patch)
treecc029e950d0384e3486ef6e3220a77300859fde2
parente0975b2aae0e669f995f7d5f11db25c3080ae11c (diff)
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 <ktkhai@virtuozzo.com> Acked-by: Cyrill Gorcunov <gorcunov@gmail.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/ksm.c10
1 files changed, 8 insertions, 2 deletions
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;
}