From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: [PATCH v3] ksm: React on changing "sleep_millisecs" parameter faster From: Kirill Tkhai Date: Tue, 11 Dec 2018 18:11:25 +0300 Message-ID: <154454107680.3258.3558002210423531566.stgit@localhost.localdomain> In-Reply-To: <2dd9cc7b-9384-df11-bb5a-3aed45cc914b@virtuozzo.com> References: <2dd9cc7b-9384-df11-bb5a-3aed45cc914b@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org To: akpm@linux-foundation.org, mhocko@suse.com, ktkhai@virtuozzo.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, gorcunov@virtuozzo.com List-ID: 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. Signed-off-by: Kirill Tkhai v3: Do not use mutex: to acquire it may take much time in case long list of ksm'able mm and pages. v2: Use wait_event_interruptible_timeout() instead of unconditional schedule_timeout(). --- mm/ksm.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index daa14db01e4d..383f961e577a 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); @@ -2412,6 +2413,8 @@ static int ksmd_should_run(void) static int ksm_scan_thread(void *nothing) { + unsigned int sleep_ms; + set_freezable(); set_user_nice(current, 5); @@ -2425,8 +2428,10 @@ 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()); @@ -2845,6 +2850,7 @@ static ssize_t sleep_millisecs_store(struct kobject *kobj, return -EINVAL; ksm_thread_sleep_millisecs = msecs; + wake_up_interruptible(&ksm_iter_wait); return count; }