[PATCH 7/9] kstaled: add histogram sampling functionality

Michel Lespinasse
2011-09-28T00:49:45Z

Add statistics for pages that have been idle for 1,2,5,15,30,60,120 or
240 scan intervals into /dev/cgroup/*/memory.idle_page_stats

Signed-off-by: Michel Lespinasse <walken@google.com>
---
include/linux/mmzone.h | 2 +
mm/memcontrol.c | 108 ++++++++++++++++++++++++++++++++++++++----------
mm/memory_hotplug.c | 6 +++
3 files changed, 94 insertions(+), 22 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 272fbed..d8eca1b 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -633,6 +633,8 @@ typedef struct pglist_data {
range, including holes */
#ifdef CONFIG_KSTALED
unsigned long node_idle_scan_pfn;
+ u8 *node_idle_page_age; /* number of scan intervals since
+ each page was referenced */
#endif
int node_id;
wait_queue_head_t kswapd_wait;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b468867..cfe812b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -207,6 +207,11 @@ struct mem_cgroup_eventfd_list {
static void mem_cgroup_threshold(struct mem_cgroup *mem);
static void mem_cgroup_oom_notify(struct mem_cgroup *mem);

+#ifdef CONFIG_KSTALED
+static const int kstaled_buckets[] = {1, 2, 5, 15, 30, 60, 120, 240};
+#define NUM_KSTALED_BUCKETS ARRAY_SIZE(kstaled_buckets)
+#endif
+
/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
@@ -292,7 +297,8 @@ struct mem_cgroup {
unsigned long idle_clean;
unsigned long idle_dirty_file;
unsigned long idle_dirty_swap;
- } idle_page_stats, idle_scan_stats;
+ } idle_page_stats[NUM_KSTALED_BUCKETS],
+ idle_scan_stats[NUM_KSTALED_BUCKETS];
unsigned long idle_page_scans;
#endif
};
@@ -4686,18 +4692,29 @@ static int mem_cgroup_idle_page_stats_read(struct cgroup *cgrp,
{
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
unsigned int seqcount;
- struct idle_page_stats stats;
+ struct idle_page_stats stats[NUM_KSTALED_BUCKETS];
unsigned long scans;
+ int bucket;

do {
seqcount = read_seqcount_begin(&memcg->idle_page_stats_lock);
- stats = memcg->idle_page_stats;
+ memcpy(stats, memcg->idle_page_stats, sizeof(stats));
scans = memcg->idle_page_scans;
} while (read_seqcount_retry(&memcg->idle_page_stats_lock, seqcount));

- cb->fill(cb, "idle_clean", stats.idle_clean * PAGE_SIZE);
- cb->fill(cb, "idle_dirty_file", stats.idle_dirty_file * PAGE_SIZE);
- cb->fill(cb, "idle_dirty_swap", stats.idle_dirty_swap * PAGE_SIZE);
+ for (bucket = 0; bucket < NUM_KSTALED_BUCKETS; bucket++) {
+ char basename[32], name[32];
+ if (!bucket)
+ sprintf(basename, "idle");
+ else
+ sprintf(basename, "idle_%d", kstaled_buckets[bucket]);
+ sprintf(name, "%s_clean", basename);
+ cb->fill(cb, name, stats[bucket].idle_clean * PAGE_SIZE);
+ sprintf(name, "%s_dirty_file", basename);
+ cb->fill(cb, name, stats[bucket].idle_dirty_file * PAGE_SIZE);
+ sprintf(name, "%s_dirty_swap", basename);
+ cb->fill(cb, name, stats[bucket].idle_dirty_swap * PAGE_SIZE);
+ }
cb->fill(cb, "scans", scans);

return 0;
@@ -5619,12 +5636,25 @@ __setup("swapaccount=", enable_swap_account);
static unsigned int kstaled_scan_seconds;
static DECLARE_WAIT_QUEUE_HEAD(kstaled_wait);

-static unsigned kstaled_scan_page(struct page *page)
+static inline struct idle_page_stats *
+kstaled_idle_stats(struct mem_cgroup *memcg, int age)
+{
+ int bucket = 0;
+
+ while (age >= kstaled_buckets[bucket + 1])
+ if (++bucket == NUM_KSTALED_BUCKETS - 1)
+ break;
+ return memcg->idle_scan_stats + bucket;
+}
+
+static unsigned kstaled_scan_page(struct page *page, u8 *idle_page_age)
{
bool is_locked = false;
bool is_file;
struct page_referenced_info info;
struct page_cgroup *pc;
+ struct mem_cgroup *memcg;
+ int age;
struct idle_page_stats *stats;
unsigned nr_pages;

@@ -5704,17 +5734,25 @@ static unsigned kstaled_scan_page(struct page *page)

/* Find out if the page is idle. Also test for pending mlock. */
page_referenced_kstaled(page, is_locked, &info);
- if ((info.pr_flags & PR_REFERENCED) || (info.vm_flags & VM_LOCKED))
+ if ((info.pr_flags & PR_REFERENCED) || (info.vm_flags & VM_LOCKED)) {
+ *idle_page_age = 0;
goto out;
+ }

/* Locate kstaled stats for the page's cgroup. */
pc = lookup_page_cgroup(page);
if (!pc)
goto out;
lock_page_cgroup(pc);
+ memcg = pc->mem_cgroup;
if (!PageCgroupUsed(pc))
goto unlock_page_cgroup_out;
- stats = &pc->mem_cgroup->idle_scan_stats;
+
+ /* Page is idle, increment its age and get the right stats bucket */
+ age = *idle_page_age;
+ if (age < 255)
+ *idle_page_age = ++age;
+ stats = kstaled_idle_stats(memcg, age);

/* Finally increment the correct statistic for this page. */
if (!(info.pr_flags & PR_DIRTY) &&
@@ -5740,11 +5778,22 @@ static bool kstaled_scan_node(pg_data_t *pgdat, int scan_seconds, bool reset)
{
unsigned long flags;
unsigned long pfn, end, node_end;
+ u8 *idle_page_age;

pgdat_resize_lock(pgdat, &flags);

+ if (!pgdat->node_idle_page_age) {
+ pgdat->node_idle_page_age = vmalloc(pgdat->node_spanned_pages);
+ if (!pgdat->node_idle_page_age) {
+ pgdat_resize_unlock(pgdat, &flags);
+ return false;
+ }
+ memset(pgdat->node_idle_page_age, 0, pgdat->node_spanned_pages);
+ }
+
pfn = pgdat->node_start_pfn;
node_end = pfn + pgdat->node_spanned_pages;
+ idle_page_age = pgdat->node_idle_page_age - pfn;
if (!reset && pfn < pgdat->node_idle_scan_pfn)
pfn = pgdat->node_idle_scan_pfn;
end = min(pfn + DIV_ROUND_UP(pgdat->node_spanned_pages, scan_seconds),
@@ -5766,13 +5815,15 @@ static bool kstaled_scan_node(pg_data_t *pgdat, int scan_seconds, bool reset)
/* abort if the node got resized */
if (pfn < pgdat->node_start_pfn ||
node_end > (pgdat->node_start_pfn +
- pgdat->node_spanned_pages))
+ pgdat->node_spanned_pages) ||
+ !pgdat->node_idle_page_age)
goto abort;
#endif
}

pfn += pfn_valid(pfn) ?
- kstaled_scan_page(pfn_to_page(pfn)) : 1;
+ kstaled_scan_page(pfn_to_page(pfn),
+ idle_page_age + pfn) : 1;
}
}

@@ -5783,6 +5834,28 @@ abort:
return pfn >= node_end;
}

+static void kstaled_update_stats(struct mem_cgroup *memcg)
+{
+ struct idle_page_stats tot;
+ int i;
+
+ memset(&tot, 0, sizeof(tot));
+
+ write_seqcount_begin(&memcg->idle_page_stats_lock);
+ for (i = NUM_KSTALED_BUCKETS - 1; i >= 0; i--) {
+ struct idle_page_stats *idle_scan_bucket;
+ idle_scan_bucket = memcg->idle_scan_stats + i;
+ tot.idle_clean += idle_scan_bucket->idle_clean;
+ tot.idle_dirty_file += idle_scan_bucket->idle_dirty_file;
+ tot.idle_dirty_swap += idle_scan_bucket->idle_dirty_swap;
+ memcg->idle_page_stats[i] = tot;
+ }
+ memcg->idle_page_scans++;
+ write_seqcount_end(&memcg->idle_page_stats_lock);
+
+ memset(&memcg->idle_scan_stats, 0, sizeof(memcg->idle_scan_stats));
+}
+
static int kstaled(void *dummy)
{
bool reset = true;
@@ -5819,17 +5892,8 @@ static int kstaled(void *dummy)
if (scan_done) {
struct mem_cgroup *memcg;

- for_each_mem_cgroup_all(memcg) {
- write_seqcount_begin(
- &memcg->idle_page_stats_lock);
- memcg->idle_page_stats =
- memcg->idle_scan_stats;
- memcg->idle_page_scans++;
- write_seqcount_end(
- &memcg->idle_page_stats_lock);
- memset(&memcg->idle_scan_stats, 0,
- sizeof(memcg->idle_scan_stats));
- }
+ for_each_mem_cgroup_all(memcg)
+ kstaled_update_stats(memcg);
}

delta = jiffies - deadline;
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index c46887b..0b490ac 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -211,6 +211,12 @@ static void grow_pgdat_span(struct pglist_data *pgdat, unsigned long start_pfn,

pgdat->node_spanned_pages = max(old_pgdat_end_pfn, end_pfn) -
pgdat->node_start_pfn;
+#ifdef CONFIG_KSTALED
+ if (pgdat->node_idle_page_age) {
+ vfree(pgdat->node_idle_page_age);
+ pgdat->node_idle_page_age = NULL;
+ }
+#endif
}

static int __meminit __add_zone(struct zone *zone, unsigned long phys_start_pfn)
--
1.7.3.1