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@google.com --- 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 = {