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mm/ksm: add sysfs knobs for advisor

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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: Stefan Roesch <shr@devkernel.io>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Stefan Roesch 2023-12-18 15:10:52 -08:00 committed by Andrew Morton
parent 4e5fa4f5ef
commit 66790e9a73
1 changed files with 148 additions and 0 deletions
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148
mm/ksm.c
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@ -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,
};