The refresh interval is a rate limiting factor to workingset page age
histogram reads. When a workingset report is generated, a timestamp
is noted, and the same report will be read until it expires beyond
the refresh interval, at which point a new report is generated.
Sysfs interface
/sys/devices/system/node/nodeX/workingset_report/refresh_interval
time in milliseconds specifying how long the report is valid for
Signed-off-by: Yuanchu Xie <yuanchu@xxxxxxxxxx>
---
include/linux/workingset_report.h | 1 +
mm/workingset_report.c | 84 +++++++++++++++++++++++++------
2 files changed, 70 insertions(+), 15 deletions(-)
diff --git a/include/linux/workingset_report.h b/include/linux/workingset_report.h
index d7c2ee14ec87..8bae6a600410 100644
--- a/include/linux/workingset_report.h
+++ b/include/linux/workingset_report.h
@@ -37,6 +37,7 @@ struct wsr_page_age_histo {
};
struct wsr_state {
+ unsigned long refresh_interval;
/* breakdown of workingset by page age */
struct mutex page_age_lock;
struct wsr_page_age_histo *page_age;
diff --git a/mm/workingset_report.c b/mm/workingset_report.c
index a4dcf62fcd96..fe553c0a653e 100644
--- a/mm/workingset_report.c
+++ b/mm/workingset_report.c
@@ -195,7 +195,8 @@ static void collect_page_age(struct wsr_page_age_histo *page_age,
/* First step: hierarchically scan child memcgs. */
static void refresh_scan(struct wsr_state *wsr, struct mem_cgroup *root,
- struct pglist_data *pgdat)
+ struct pglist_data *pgdat,
+ unsigned long refresh_interval)
{
struct mem_cgroup *memcg;
unsigned int flags;
@@ -208,12 +209,15 @@ static void refresh_scan(struct wsr_state *wsr, struct mem_cgroup *root,
do {
struct lruvec *lruvec = mem_cgroup_lruvec(memcg, pgdat);
unsigned long max_seq = READ_ONCE((lruvec)->lrugen.max_seq);
+ int gen = lru_gen_from_seq(max_seq);
+ unsigned long birth = READ_ONCE(lruvec->lrugen.timestamps[gen]);
/*
* setting can_swap=true and force_scan=true ensures
* proper workingset stats when the system cannot swap.
*/
- try_to_inc_max_seq(lruvec, max_seq, true, true);
+ if (time_is_before_jiffies(birth + refresh_interval))
+ try_to_inc_max_seq(lruvec, max_seq, true, true);
cond_resched();
} while ((memcg = mem_cgroup_iter(root, memcg, NULL)));
@@ -270,17 +274,25 @@ bool wsr_refresh_report(struct wsr_state *wsr, struct mem_cgroup *root,
struct pglist_data *pgdat)
{
struct wsr_page_age_histo *page_age;
+ unsigned long refresh_interval = READ_ONCE(wsr->refresh_interval);
if (!READ_ONCE(wsr->page_age))
return false;
- refresh_scan(wsr, root, pgdat);
+ if (!refresh_interval)
+ return false;
+
mutex_lock(&wsr->page_age_lock);
page_age = READ_ONCE(wsr->page_age);
- if (page_age) {
- copy_node_bins(pgdat, page_age);
- refresh_aggregate(page_age, root, pgdat);
- }
+ if (!page_age)
+ goto unlock;
+ if (page_age->timestamp &&
+ time_is_after_jiffies(page_age->timestamp + refresh_interval))
+ goto unlock;
+ refresh_scan(wsr, root, pgdat, refresh_interval);
+ copy_node_bins(pgdat, page_age);
+ refresh_aggregate(page_age, root, pgdat);
+unlock:
mutex_unlock(&wsr->page_age_lock);
return !!page_age;
}
@@ -299,6 +311,52 @@ static struct wsr_state *kobj_to_wsr(struct kobject *kobj)
return &mem_cgroup_lruvec(NULL, kobj_to_pgdat(kobj))->wsr;
}
+static ssize_t refresh_interval_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ struct wsr_state *wsr = kobj_to_wsr(kobj);
+ unsigned int interval = READ_ONCE(wsr->refresh_interval);
+
+ return sysfs_emit(buf, "%u\n", jiffies_to_msecs(interval));
+}
+
+static ssize_t refresh_interval_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t len)
+{
+ unsigned int interval;
+ int err;
+ struct wsr_state *wsr = kobj_to_wsr(kobj);
+
+ err = kstrtouint(buf, 0, &interval);
+ if (err)
+ return err;
+
+ mutex_lock(&wsr->page_age_lock);
+ if (interval && !wsr->page_age) {
+ struct wsr_page_age_histo *page_age =
+ kzalloc(sizeof(struct wsr_page_age_histo), GFP_KERNEL);
+
+ if (!page_age) {
+ err = -ENOMEM;
+ goto unlock;
+ }
+ wsr->page_age = page_age;
+ }
+ if (!interval && wsr->page_age) {
+ kfree(wsr->page_age);
+ wsr->page_age = NULL;
+ }
+
+ WRITE_ONCE(wsr->refresh_interval, msecs_to_jiffies(interval));
+unlock:
+ mutex_unlock(&wsr->page_age_lock);
+ return err ?: len;
+}
+
+static struct kobj_attribute refresh_interval_attr =
+ __ATTR_RW(refresh_interval);
+
static ssize_t page_age_intervals_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
@@ -382,13 +440,6 @@ static ssize_t page_age_show(struct kobject *kobj, struct kobj_attribute *attr,
int ret = 0;
struct wsr_state *wsr = kobj_to_wsr(kobj);
-
- mutex_lock(&wsr->page_age_lock);
- if (!wsr->page_age)
- wsr->page_age =
- kzalloc(sizeof(struct wsr_page_age_histo), GFP_KERNEL);
- mutex_unlock(&wsr->page_age_lock);
-
wsr_refresh_report(wsr, NULL, kobj_to_pgdat(kobj));
mutex_lock(&wsr->page_age_lock);
@@ -414,7 +465,10 @@ static ssize_t page_age_show(struct kobject *kobj, struct kobj_attribute *attr,
static struct kobj_attribute page_age_attr = __ATTR_RO(page_age);
static struct attribute *workingset_report_attrs[] = {
- &page_age_intervals_attr.attr, &page_age_attr.attr, NULL
+ &refresh_interval_attr.attr,
+ &page_age_intervals_attr.attr,
+ &page_age_attr.attr,
+ NULL
};
static const struct attribute_group workingset_report_attr_group = {
--
2.45.1.467.gbab1589fc0-goog
