Commit 66790e9a authored by Stefan Roesch's avatar Stefan Roesch Committed by Andrew Morton
Browse files

mm/ksm: add sysfs knobs for advisor 

This adds four new knobs for the KSM advisor to influence its behaviour.

The knobs are:
- advisor_mode:
    none:      no advisor (default)
    scan-time: scan time advisor
- advisor_max_cpu: 70 (default, cpu usage percent)
- advisor_min_pages_to_scan: 500 (default)
- advisor_max_pages_to_scan: 30000 (default)
- advisor_target_scan_time: 200 (default in seconds)

The new values will take effect on the next scan round.

Link: https://lkml.kernel.org/r/20231218231054.1625219-3-shr@devkernel.io


Signed-off-by: default avatarStefan Roesch <shr@devkernel.io>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4e5fa4f5

mm/ksm.c

+148 −0
Original line number Diff line number Diff line
@@ -338,6 +338,25 @@ enum ksm_advisor_type { 
};

static enum ksm_advisor_type ksm_advisor;



#ifdef CONFIG_SYSFS

/*

 * Only called through the sysfs control interface:

 */



/* At least scan this many pages per batch. */

static unsigned long ksm_advisor_min_pages_to_scan = 500;



static void set_advisor_defaults(void)

{

	if (ksm_advisor == KSM_ADVISOR_NONE) {

		ksm_thread_pages_to_scan = DEFAULT_PAGES_TO_SCAN;

	} else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME) {

		advisor_ctx = (const struct advisor_ctx){ 0 };

		ksm_thread_pages_to_scan = ksm_advisor_min_pages_to_scan;

	}

}

#endif /* CONFIG_SYSFS */



static inline void advisor_start_scan(void)

{

	if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)
@@ -3721,6 +3740,130 @@ static ssize_t smart_scan_store(struct kobject *kobj, 
}

KSM_ATTR(smart_scan);



static ssize_t advisor_mode_show(struct kobject *kobj,

				 struct kobj_attribute *attr, char *buf)

{

	const char *output;



	if (ksm_advisor == KSM_ADVISOR_NONE)

		output = "[none] scan-time";

	else if (ksm_advisor == KSM_ADVISOR_SCAN_TIME)

		output = "none [scan-time]";



	return sysfs_emit(buf, "%s\n", output);

}



static ssize_t advisor_mode_store(struct kobject *kobj,

				  struct kobj_attribute *attr, const char *buf,

				  size_t count)

{

	enum ksm_advisor_type curr_advisor = ksm_advisor;



	if (sysfs_streq("scan-time", buf))

		ksm_advisor = KSM_ADVISOR_SCAN_TIME;

	else if (sysfs_streq("none", buf))

		ksm_advisor = KSM_ADVISOR_NONE;

	else

		return -EINVAL;



	/* Set advisor default values */

	if (curr_advisor != ksm_advisor)

		set_advisor_defaults();



	return count;

}

KSM_ATTR(advisor_mode);



static ssize_t advisor_max_cpu_show(struct kobject *kobj,

				    struct kobj_attribute *attr, char *buf)

{

	return sysfs_emit(buf, "%u\n", ksm_advisor_max_cpu);

}



static ssize_t advisor_max_cpu_store(struct kobject *kobj,

				     struct kobj_attribute *attr,

				     const char *buf, size_t count)

{

	int err;

	unsigned long value;



	err = kstrtoul(buf, 10, &value);

	if (err)

		return -EINVAL;



	ksm_advisor_max_cpu = value;

	return count;

}

KSM_ATTR(advisor_max_cpu);



static ssize_t advisor_min_pages_to_scan_show(struct kobject *kobj,

					struct kobj_attribute *attr, char *buf)

{

	return sysfs_emit(buf, "%lu\n", ksm_advisor_min_pages_to_scan);

}



static ssize_t advisor_min_pages_to_scan_store(struct kobject *kobj,

					struct kobj_attribute *attr,

					const char *buf, size_t count)

{

	int err;

	unsigned long value;



	err = kstrtoul(buf, 10, &value);

	if (err)

		return -EINVAL;



	ksm_advisor_min_pages_to_scan = value;

	return count;

}

KSM_ATTR(advisor_min_pages_to_scan);



static ssize_t advisor_max_pages_to_scan_show(struct kobject *kobj,

					struct kobj_attribute *attr, char *buf)

{

	return sysfs_emit(buf, "%lu\n", ksm_advisor_max_pages_to_scan);

}



static ssize_t advisor_max_pages_to_scan_store(struct kobject *kobj,

					struct kobj_attribute *attr,

					const char *buf, size_t count)

{

	int err;

	unsigned long value;



	err = kstrtoul(buf, 10, &value);

	if (err)

		return -EINVAL;



	ksm_advisor_max_pages_to_scan = value;

	return count;

}

KSM_ATTR(advisor_max_pages_to_scan);



static ssize_t advisor_target_scan_time_show(struct kobject *kobj,

					     struct kobj_attribute *attr, char *buf)

{

	return sysfs_emit(buf, "%lu\n", ksm_advisor_target_scan_time);

}



static ssize_t advisor_target_scan_time_store(struct kobject *kobj,

					      struct kobj_attribute *attr,

					      const char *buf, size_t count)

{

	int err;

	unsigned long value;



	err = kstrtoul(buf, 10, &value);

	if (err)

		return -EINVAL;

	if (value < 1)

		return -EINVAL;



	ksm_advisor_target_scan_time = value;

	return count;

}

KSM_ATTR(advisor_target_scan_time);



static struct attribute *ksm_attrs[] = {

	&sleep_millisecs_attr.attr,

	&pages_to_scan_attr.attr,
@@ -3743,6 +3886,11 @@ static struct attribute *ksm_attrs[] = { 
	&use_zero_pages_attr.attr,

	&general_profit_attr.attr,

	&smart_scan_attr.attr,

	&advisor_mode_attr.attr,

	&advisor_max_cpu_attr.attr,

	&advisor_min_pages_to_scan_attr.attr,

	&advisor_max_pages_to_scan_attr.attr,

	&advisor_target_scan_time_attr.attr,

	NULL,

};