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Subject[RFC][PATCH v3 8/10] memcg: scan ratio calculation

==
This patch adds a function to calculate reclam/scan ratio.
By the recent scan.
This wil be shown by memory.reclaim_stat interface in later patch.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
include/linux/swap.h | 8 +-
mm/memcontrol.c | 137 +++++++++++++++++++++++++++++++++++++++++++++++----
mm/vmscan.c | 9 ++-
3 files changed, 138 insertions(+), 16 deletions(-)

Index: memcg_async/mm/memcontrol.c
===================================================================
--- memcg_async.orig/mm/memcontrol.c
+++ memcg_async/mm/memcontrol.c
@@ -73,7 +73,6 @@ static int really_do_swap_account __init
#define do_swap_account (0)
#endif

-
/*
* Statistics for memory cgroup.
*/
@@ -215,6 +214,7 @@ static void mem_cgroup_oom_notify(struct
static void mem_cgroup_reset_margin_to_limit(struct mem_cgroup *mem);
static void mem_cgroup_update_margin_to_limit(struct mem_cgroup *mem);
static void mem_cgroup_may_async_reclaim(struct mem_cgroup *mem);
+static void mem_cgroup_reflesh_scan_ratio(struct mem_cgroup *mem);

/*
* The memory controller data structure. The memory controller controls both
@@ -294,6 +294,12 @@ struct mem_cgroup {
#define FAILED_TO_KEEP_MARGIN (1) /* someone hit limit */
#define ASYNC_WORKER_RUNNING (2) /* a worker runs */
#define ASYNC_WORKER_SHOULD_STOP (3) /* worker thread should stop */
+
+ /* For calculating scan success ratio */
+ spinlock_t scan_stat_lock;
+ unsigned long scanned;
+ unsigned long reclaimed;
+ unsigned long next_scanratio_update;
/*
* percpu counter.
*/
@@ -758,6 +764,7 @@ static void memcg_check_events(struct me
}
/* update margin-to-limit and run async reclaim if necessary */
if (__memcg_event_check(mem, MEM_CGROUP_TARGET_KEEP_MARGIN)) {
+ mem_cgroup_reflesh_scan_ratio(mem);
mem_cgroup_may_async_reclaim(mem);
__mem_cgroup_target_update(mem,
MEM_CGROUP_TARGET_KEEP_MARGIN);
@@ -1417,6 +1424,96 @@ unsigned int mem_cgroup_swappiness(struc
return memcg->swappiness;
}

+static void __mem_cgroup_update_scan_ratio(struct mem_cgroup *mem,
+ unsigned long scanned,
+ unsigned long reclaimed)
+{
+ unsigned long limit;
+
+ limit = res_counter_read_u64(&mem->res, RES_LIMIT) >> PAGE_SHIFT;
+ spin_lock(&mem->scan_stat_lock);
+ mem->scanned += scanned;
+ mem->reclaimed += reclaimed;
+ /* avoid overflow */
+ if (mem->scanned > limit) {
+ mem->scanned /= 2;
+ mem->reclaimed /= 2;
+ }
+ spin_unlock(&mem->scan_stat_lock);
+}
+
+/**
+ * mem_cgroup_update_scan_ratio
+ * @memcg: the memcg
+ * @root : root memcg of hierarchy walk.
+ * @scanned : scanned pages
+ * @reclaimed: reclaimed pages.
+ *
+ * record scan/reclaim ratio to the memcg both to a child and it's root
+ * mem cgroup, which is a reclaim target. This value is used for
+ * detect congestion and for determining sleep time at memory reclaim.
+ */
+
+static void mem_cgroup_update_scan_ratio(struct mem_cgroup *mem,
+ struct mem_cgroup *root,
+ unsigned long scanned,
+ unsigned long reclaimed)
+{
+ __mem_cgroup_update_scan_ratio(mem, scanned, reclaimed);
+ if (mem != root)
+ __mem_cgroup_update_scan_ratio(root, scanned, reclaimed);
+
+}
+
+/*
+ * Workload can be changed over time. This routine is for forgetting old
+ * information to some extent. This is triggered by event counter i.e.
+ * some amounts of pagein/pageout events and rate limited once per 1 min.
+ *
+ * By this, recent 1min information will be twice informative than old
+ * information.
+ */
+static void mem_cgroup_reflesh_scan_ratio(struct mem_cgroup *mem)
+{
+ struct cgroup *parent;
+ /* Update all parent's information if they are old */
+ while (1) {
+ if (time_after(mem->next_scanratio_update, jiffies))
+ break;
+ mem->next_scanratio_update = jiffies + HZ*60;
+ spin_lock(&mem->scan_stat_lock);
+ mem->scanned /= 2;
+ mem->reclaimed /= 2;
+ spin_unlock(&mem->scan_stat_lock);
+ if (!mem->use_hierarchy)
+ break;
+ parent = mem->css.cgroup->parent;
+ if (!parent)
+ break;
+ mem = mem_cgroup_from_cont(parent);
+ }
+}
+
+/**
+ * mem_cgroup_scan_ratio:
+ * @mem: the mem cgroup
+ *
+ * Returns recent reclaim/scan ratio. If this is low, memory is filled by
+ * active pages(or dirty pages). If high, memory includes inactive, unneccesary
+ * files. This can be a hint for admins to show the limit is correct or not.
+ */
+static int mem_cgroup_scan_ratio(struct mem_cgroup *mem)
+{
+ int scan_success_ratio;
+
+ spin_lock(&mem->scan_stat_lock);
+ scan_success_ratio = mem->reclaimed * 100 / (mem->scanned + 1);
+ spin_unlock(&mem->scan_stat_lock);
+
+ return scan_success_ratio;
+}
+
+
static void mem_cgroup_start_move(struct mem_cgroup *mem)
{
int cpu;
@@ -1855,9 +1952,14 @@ static int mem_cgroup_hierarchical_recla
*total_scanned += nr_scanned;
mem_cgroup_soft_steal(victim, is_kswapd, ret);
mem_cgroup_soft_scan(victim, is_kswapd, nr_scanned);
- } else
+ mem_cgroup_update_scan_ratio(victim,
+ root_mem, nr_scanned, ret);
+ } else {
ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
- noswap);
+ noswap, &nr_scanned);
+ mem_cgroup_update_scan_ratio(victim,
+ root_mem, nr_scanned, ret);
+ }
css_put(&victim->css);
/*
* At shrinking usage, we can't check we should stop here or
@@ -3895,12 +3997,14 @@ static void mem_cgroup_stop_async_worker
* someone tries to delete cgroup, stop reclaim.
* If margin is big even after shrink memory, reschedule itself again.
*/
+
static void mem_cgroup_async_shrink_worker(struct work_struct *work)
{
struct delayed_work *dw = to_delayed_work(work);
- struct mem_cgroup *mem;
- int delay = 0;
+ struct mem_cgroup *mem, *victim;
long nr_to_reclaim;
+ unsigned long nr_scanned, nr_reclaimed;
+ int delay = 0;

mem = container_of(dw, struct mem_cgroup, async_work);

@@ -3910,12 +4014,22 @@ static void mem_cgroup_async_shrink_work

nr_to_reclaim = mem->margin_to_limit_pages - mem_cgroup_margin(mem);

- if (nr_to_reclaim > 0)
- mem_cgroup_shrink_rate_limited(mem, nr_to_reclaim);
- else
+ if (nr_to_reclaim <= 0)
+ goto finish_scan;
+
+ /* select a memcg under hierarchy */
+ victim = mem_cgroup_select_get_victim(mem);
+ if (!victim)
goto finish_scan;
+
+ nr_reclaimed = mem_cgroup_shrink_rate_limited(victim, nr_to_reclaim,
+ &nr_scanned);
+ mem_cgroup_update_scan_ratio(victim, mem, nr_scanned, nr_reclaimed);
+ css_put(&victim->css);
+
/* If margin is enough big, stop */
- if (mem_cgroup_margin(mem) >= mem->margin_to_limit_pages)
+ nr_to_reclaim = mem->margin_to_limit_pages - mem_cgroup_margin(mem);
+ if (nr_to_reclaim <= 0)
goto finish_scan;
/* If someone tries to rmdir(), we should stop */
if (test_bit(ASYNC_WORKER_SHOULD_STOP, &mem->async_flags))
@@ -4083,12 +4197,14 @@ try_to_free:
shrink = 1;
while (nr_retries && mem->res.usage > 0) {
int progress;
+ unsigned long nr_scanned;

if (signal_pending(current)) {
ret = -EINTR;
goto out;
}
- progress = try_to_free_mem_cgroup_pages(mem, GFP_KERNEL, false);
+ progress = try_to_free_mem_cgroup_pages(mem, GFP_KERNEL,
+ false, &nr_scanned);
if (!progress) {
nr_retries--;
/* maybe some writeback is necessary */
@@ -5315,6 +5431,7 @@ mem_cgroup_create(struct cgroup_subsys *
atomic_set(&mem->refcnt, 1);
mem->move_charge_at_immigrate = 0;
spin_lock_init(&mem->update_margin_lock);
+ spin_lock_init(&mem->scan_stat_lock);
INIT_DELAYED_WORK(&mem->async_work, mem_cgroup_async_shrink_worker);
mutex_init(&mem->thresholds_lock);
return &mem->css;
Index: memcg_async/include/linux/swap.h
===================================================================
--- memcg_async.orig/include/linux/swap.h
+++ memcg_async/include/linux/swap.h
@@ -252,13 +252,15 @@ static inline void lru_cache_add_file(st
extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
gfp_t gfp_mask, nodemask_t *mask);
extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
- gfp_t gfp_mask, bool noswap);
+ gfp_t gfp_mask, bool noswap,
+ unsigned long *nr_scanned);
extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
gfp_t gfp_mask, bool noswap,
struct zone *zone,
unsigned long *nr_scanned);
-extern void mem_cgroup_shrink_rate_limited(struct mem_cgroup *mem,
- unsigned long nr_to_reclaim);
+extern unsigned long mem_cgroup_shrink_rate_limited(struct mem_cgroup *mem,
+ unsigned long nr_to_reclaim,
+ unsigned long *nr_scanned);

extern int __isolate_lru_page(struct page *page, int mode, int file);
extern unsigned long shrink_all_memory(unsigned long nr_pages);
Index: memcg_async/mm/vmscan.c
===================================================================
--- memcg_async.orig/mm/vmscan.c
+++ memcg_async/mm/vmscan.c
@@ -2221,7 +2221,8 @@ unsigned long mem_cgroup_shrink_node_zon

unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
gfp_t gfp_mask,
- bool noswap)
+ bool noswap,
+ unsigned long *nr_scanned)
{
struct zonelist *zonelist;
unsigned long nr_reclaimed;
@@ -2258,12 +2259,14 @@ unsigned long try_to_free_mem_cgroup_pag
nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);

trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);
+ *nr_scanned = sc.nr_scanned;

return nr_reclaimed;
}

-void mem_cgroup_shrink_rate_limited(struct mem_cgroup *mem,
- unsigned long nr_to_reclaim)
+unsigned long mem_cgroup_shrink_rate_limited(struct mem_cgroup *mem,
+ unsigned long nr_to_reclaim,
+ unsigned long *nr_scanned)
{
}



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