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Subject[RFC][PATCH v3 10/10] memcg : reclaim statistics

This patch adds a file memory.reclaim_stat.

This file shows following.
==
recent_scan_success_ratio 12 # recent reclaim/scan ratio.
limit_scan_pages 671 # scan caused by hitting limit.
limit_freed_pages 538 # freed pages by limit_scan
limit_elapsed_ns 518555076 # elapsed time in LRU scanning by limit.
soft_scan_pages 0 # scan caused by softlimit.
soft_freed_pages 0 # freed pages by soft_scan.
soft_elapsed_ns 0 # elapsed time in LRU scanning by softlimit.
margin_scan_pages 16744221 # scan caused by auto-keep-margin
margin_freed_pages 565943 # freed pages by auto-keep-margin.
margin_elapsed_ns 5545388791 # elapsed time in LRU scanning by auto-keep-margin

This patch adds a new file rather than adding more stats to memory.stat. By it,
this support "reset" accounting by

# echo 0 > .../memory.reclaim_stat

This is good for debug and tuning.

TODO:
- add Documentaion.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
mm/memcontrol.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 79 insertions(+), 8 deletions(-)

Index: memcg_async/mm/memcontrol.c
===================================================================
--- memcg_async.orig/mm/memcontrol.c
+++ memcg_async/mm/memcontrol.c
@@ -216,6 +216,13 @@ static void mem_cgroup_update_margin_to_
static void mem_cgroup_may_async_reclaim(struct mem_cgroup *mem);
static void mem_cgroup_reflesh_scan_ratio(struct mem_cgroup *mem);

+enum scan_type {
+ LIMIT_SCAN, /* scan memory because memcg hits limit */
+ SOFT_SCAN, /* scan memory because of soft limit */
+ MARGIN_SCAN, /* scan memory for making margin to limit */
+ NR_SCAN_TYPES,
+};
+
/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
@@ -300,6 +307,13 @@ struct mem_cgroup {
unsigned long scanned;
unsigned long reclaimed;
unsigned long next_scanratio_update;
+ /* For statistics */
+ struct {
+ unsigned long nr_scanned_pages;
+ unsigned long nr_reclaimed_pages;
+ unsigned long elapsed_ns;
+ } scan_stat[NR_SCAN_TYPES];
+
/*
* percpu counter.
*/
@@ -1426,7 +1440,9 @@ unsigned int mem_cgroup_swappiness(struc

static void __mem_cgroup_update_scan_ratio(struct mem_cgroup *mem,
unsigned long scanned,
- unsigned long reclaimed)
+ unsigned long reclaimed,
+ unsigned long elapsed,
+ enum scan_type type)
{
unsigned long limit;

@@ -1439,6 +1455,9 @@ static void __mem_cgroup_update_scan_rat
mem->scanned /= 2;
mem->reclaimed /= 2;
}
+ mem->scan_stat[type].nr_scanned_pages += scanned;
+ mem->scan_stat[type].nr_reclaimed_pages += reclaimed;
+ mem->scan_stat[type].elapsed_ns += elapsed;
spin_unlock(&mem->scan_stat_lock);
}

@@ -1448,6 +1467,8 @@ static void __mem_cgroup_update_scan_rat
* @root : root memcg of hierarchy walk.
* @scanned : scanned pages
* @reclaimed: reclaimed pages.
+ * @elapsed: used time for memory reclaim
+ * @type : scan type as LIMIT_SCAN, SOFT_SCAN, MARGIN_SCAN.
*
* 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
@@ -1457,11 +1478,14 @@ static void __mem_cgroup_update_scan_rat
static void mem_cgroup_update_scan_ratio(struct mem_cgroup *mem,
struct mem_cgroup *root,
unsigned long scanned,
- unsigned long reclaimed)
+ unsigned long reclaimed,
+ unsigned long elapsed,
+ int type)
{
- __mem_cgroup_update_scan_ratio(mem, scanned, reclaimed);
+ __mem_cgroup_update_scan_ratio(mem, scanned, reclaimed, elapsed, type);
if (mem != root)
- __mem_cgroup_update_scan_ratio(root, scanned, reclaimed);
+ __mem_cgroup_update_scan_ratio(root, scanned, reclaimed,
+ elapsed, type);

}

@@ -1906,6 +1930,7 @@ static int mem_cgroup_hierarchical_recla
bool is_kswapd = false;
unsigned long excess;
unsigned long nr_scanned;
+ unsigned long start, end, elapsed;

excess = res_counter_soft_limit_excess(&root_mem->res) >> PAGE_SHIFT;

@@ -1947,18 +1972,24 @@ static int mem_cgroup_hierarchical_recla
}
/* we use swappiness of local cgroup */
if (check_soft) {
+ start = sched_clock();
ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
noswap, zone, &nr_scanned);
+ end = sched_clock();
+ elapsed = end - start;
*total_scanned += nr_scanned;
mem_cgroup_soft_steal(victim, is_kswapd, ret);
mem_cgroup_soft_scan(victim, is_kswapd, nr_scanned);
mem_cgroup_update_scan_ratio(victim,
- root_mem, nr_scanned, ret);
+ root_mem, nr_scanned, ret, elapsed, SOFT_SCAN);
} else {
+ start = sched_clock();
ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
noswap, &nr_scanned);
+ end = sched_clock();
+ elapsed = end - start;
mem_cgroup_update_scan_ratio(victim,
- root_mem, nr_scanned, ret);
+ root_mem, nr_scanned, ret, elapsed, LIMIT_SCAN);
}
css_put(&victim->css);
/*
@@ -4003,7 +4034,7 @@ static void mem_cgroup_async_shrink_work
struct delayed_work *dw = to_delayed_work(work);
struct mem_cgroup *mem, *victim;
long nr_to_reclaim;
- unsigned long nr_scanned, nr_reclaimed;
+ unsigned long nr_scanned, nr_reclaimed, start, end;
int delay = 0;

mem = container_of(dw, struct mem_cgroup, async_work);
@@ -4022,9 +4053,12 @@ static void mem_cgroup_async_shrink_work
if (!victim)
goto finish_scan;

+ start = sched_clock();
nr_reclaimed = mem_cgroup_shrink_rate_limited(victim, nr_to_reclaim,
&nr_scanned);
- mem_cgroup_update_scan_ratio(victim, mem, nr_scanned, nr_reclaimed);
+ end = sched_clock();
+ mem_cgroup_update_scan_ratio(victim, mem, nr_scanned, nr_reclaimed,
+ end - start, MARGIN_SCAN);
css_put(&victim->css);

/* If margin is enough big, stop */
@@ -4680,6 +4714,38 @@ static int mem_control_stat_show(struct
return 0;
}

+static int mem_cgroup_reclaim_stat_read(struct cgroup *cont, struct cftype *cft,
+ struct cgroup_map_cb *cb)
+{
+ struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
+ u64 val;
+ int i; /* for indexing scan_stat[] */
+
+ val = mem->reclaimed * 100 / mem->scanned;
+ cb->fill(cb, "recent_scan_success_ratio", val);
+ i = LIMIT_SCAN;
+ cb->fill(cb, "limit_scan_pages", mem->scan_stat[i].nr_scanned_pages);
+ cb->fill(cb, "limit_freed_pages", mem->scan_stat[i].nr_reclaimed_pages);
+ cb->fill(cb, "limit_elapsed_ns", mem->scan_stat[i].elapsed_ns);
+ i = SOFT_SCAN;
+ cb->fill(cb, "soft_scan_pages", mem->scan_stat[i].nr_scanned_pages);
+ cb->fill(cb, "soft_freed_pages", mem->scan_stat[i].nr_reclaimed_pages);
+ cb->fill(cb, "soft_elapsed_ns", mem->scan_stat[i].elapsed_ns);
+ i = MARGIN_SCAN;
+ cb->fill(cb, "margin_scan_pages", mem->scan_stat[i].nr_scanned_pages);
+ cb->fill(cb, "margin_freed_pages", mem->scan_stat[i].nr_reclaimed_pages);
+ cb->fill(cb, "margin_elapsed_ns", mem->scan_stat[i].elapsed_ns);
+ return 0;
+}
+
+static int mem_cgroup_reclaim_stat_reset(struct cgroup *cgrp, unsigned int event)
+{
+ struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
+ memset(mem->scan_stat, 0, sizeof(mem->scan_stat));
+ return 0;
+}
+
+
/*
* User flags for async_control is a subset of mem->async_flags. But
* this needs to be defined independently to hide implemation details.
@@ -5163,6 +5229,11 @@ static struct cftype mem_cgroup_files[]
.open = mem_control_numa_stat_open,
},
#endif
+ {
+ .name = "reclaim_stat",
+ .read_map = mem_cgroup_reclaim_stat_read,
+ .trigger = mem_cgroup_reclaim_stat_reset,
+ }
};

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP


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