Merge "ksm: Provide support to use deferred timers for scanner thread" (3d6e8cbc) · Commits · e / devices / android_kernel_sony_msm8994

Documentation/vm/ksm.txt

+7 −0

Original line number	Diff line number	Diff line
		@@ -87,6 +87,13 @@ pages_sharing - how many more sites are sharing them i.e. how much saved
		pages_unshared - how many pages unique but repeatedly checked for merging
		pages_volatile - how many pages changing too fast to be placed in a tree
		full_scans - how many times all mergeable areas have been scanned
		deferred_timer - whether to use deferred timers or not
		e.g. "echo 1 > /sys/kernel/mm/ksm/deferred_timer"
		Default: 0 (means, we are not using deferred timers. Users
		might want to set deferred_timer option if they donot want
		ksm thread to wakeup CPU to carryout ksm activities thus
		gaining on battery while compromising slightly on memory
		that could have been saved.)

		A high ratio of pages_sharing to pages_shared indicates good sharing, but
		a high ratio of pages_unshared to pages_sharing indicates wasted effort.

mm/ksm.c

+64 −1

Original line number	Diff line number	Diff line
		@@ -223,6 +223,9 @@ static unsigned int ksm_thread_pages_to_scan = 100;
		/* Milliseconds ksmd should sleep between batches */
		static unsigned int ksm_thread_sleep_millisecs = 20;

		/* Boolean to indicate whether to use deferred timer or not */
		static bool use_deferred_timer;

		#ifdef CONFIG_NUMA
		/* Zeroed when merging across nodes is not allowed */
		static unsigned int ksm_merge_across_nodes = 1;
		@@ -1706,6 +1709,41 @@ static void ksm_do_scan(unsigned int scan_npages)
		}
		}

		static void process_timeout(unsigned long __data)
		{
		wake_up_process((struct task_struct *)__data);
		}

		static signed long __sched deferred_schedule_timeout(signed long timeout)
		{
		struct timer_list timer;
		unsigned long expire;

		__set_current_state(TASK_INTERRUPTIBLE);
		if (timeout < 0) {
		pr_err("schedule_timeout: wrong timeout value %lx\n",
		timeout);
		__set_current_state(TASK_RUNNING);
		goto out;
		}

		expire = timeout + jiffies;

		setup_deferrable_timer_on_stack(&timer, process_timeout,
		(unsigned long)current);
		mod_timer(&timer, expire);
		schedule();
		del_singleshot_timer_sync(&timer);

		/* Remove the timer from the object tracker */
		destroy_timer_on_stack(&timer);

		timeout = expire - jiffies;

		out:
		return timeout < 0 ? 0 : timeout;
		}

		static int ksmd_should_run(void)
		{
		return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_list);
		@@ -1726,6 +1764,10 @@ static int ksm_scan_thread(void *nothing)
		try_to_freeze();

		if (ksmd_should_run()) {
		if (use_deferred_timer)
		deferred_schedule_timeout(
		msecs_to_jiffies(ksm_thread_sleep_millisecs));
		else
		schedule_timeout_interruptible(
		msecs_to_jiffies(ksm_thread_sleep_millisecs));
		} else {
		@@ -2275,6 +2317,26 @@ static ssize_t run_store(struct kobject kobj, struct kobj_attribute attr,
		}
		KSM_ATTR(run);

		static ssize_t deferred_timer_show(struct kobject *kobj,
		struct kobj_attribute attr, char buf)
		{
		return snprintf(buf, 8, "%d\n", use_deferred_timer);
		}

		static ssize_t deferred_timer_store(struct kobject *kobj,
		struct kobj_attribute *attr,
		const char *buf, size_t count)
		{
		unsigned long enable;
		int err;

		err = kstrtoul(buf, 10, &enable);
		use_deferred_timer = enable;

		return count;
		}
		KSM_ATTR(deferred_timer);

		#ifdef CONFIG_NUMA
		static ssize_t merge_across_nodes_show(struct kobject *kobj,
		struct kobj_attribute attr, char buf)
		@@ -2387,6 +2449,7 @@ static struct attribute *ksm_attrs[] = {
		&pages_unshared_attr.attr,
		&pages_volatile_attr.attr,
		&full_scans_attr.attr,
		&deferred_timer_attr.attr,
		#ifdef CONFIG_NUMA
		&merge_across_nodes_attr.attr,
		#endif