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memcg: add memory.vmscan_stat
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The commit log of 0ae5e89 ("memcg: count the soft_limit reclaim
in...") says it adds scanning stats to memory.stat file.  But it doesn't
because we considered we needed to make a concensus for such new APIs.

This patch is a trial to add memory.scan_stat. This shows
  - the number of scanned pages(total, anon, file)
  - the number of rotated pages(total, anon, file)
  - the number of freed pages(total, anon, file)
  - the number of elaplsed time (including sleep/pause time)

  for both of direct/soft reclaim.

The biggest difference with oringinal Ying's one is that this file
can be reset by some write, as

  # echo 0 ...../memory.scan_stat

Example of output is here. This is a result after make -j 6 kernel
under 300M limit.

  [kamezawa@bluextal ~]$ cat /cgroup/memory/A/memory.scan_stat
  [kamezawa@bluextal ~]$ cat /cgroup/memory/A/memory.vmscan_stat
  scanned_pages_by_limit 9471864
  scanned_anon_pages_by_limit 6640629
  scanned_file_pages_by_limit 2831235
  rotated_pages_by_limit 4243974
  rotated_anon_pages_by_limit 3971968
  rotated_file_pages_by_limit 272006
  freed_pages_by_limit 2318492
  freed_anon_pages_by_limit 962052
  freed_file_pages_by_limit 1356440
  elapsed_ns_by_limit 351386416101
  scanned_pages_by_system 0
  scanned_anon_pages_by_system 0
  scanned_file_pages_by_system 0
  rotated_pages_by_system 0
  rotated_anon_pages_by_system 0
  rotated_file_pages_by_system 0
  freed_pages_by_system 0
  freed_anon_pages_by_system 0
  freed_file_pages_by_system 0
  elapsed_ns_by_system 0
  scanned_pages_by_limit_under_hierarchy 9471864
  scanned_anon_pages_by_limit_under_hierarchy 6640629
  scanned_file_pages_by_limit_under_hierarchy 2831235
  rotated_pages_by_limit_under_hierarchy 4243974
  rotated_anon_pages_by_limit_under_hierarchy 3971968
  rotated_file_pages_by_limit_under_hierarchy 272006
  freed_pages_by_limit_under_hierarchy 2318492
  freed_anon_pages_by_limit_under_hierarchy 962052
  freed_file_pages_by_limit_under_hierarchy 1356440
  elapsed_ns_by_limit_under_hierarchy 351386416101
  scanned_pages_by_system_under_hierarchy 0
  scanned_anon_pages_by_system_under_hierarchy 0
  scanned_file_pages_by_system_under_hierarchy 0
  rotated_pages_by_system_under_hierarchy 0
  rotated_anon_pages_by_system_under_hierarchy 0
  rotated_file_pages_by_system_under_hierarchy 0
  freed_pages_by_system_under_hierarchy 0
  freed_anon_pages_by_system_under_hierarchy 0
  freed_file_pages_by_system_under_hierarchy 0
  elapsed_ns_by_system_under_hierarchy 0

total_xxxx is for hierarchy management.

This will be useful for further memcg developments and need to be
developped before we do some complicated rework on LRU/softlimit
management.

This patch adds a new struct memcg_scanrecord into scan_control struct.
sc->nr_scanned at el is not designed for exporting information.  For
example, nr_scanned is reset frequentrly and incremented +2 at scanning
mapped pages.

To avoid complexity, I added a new param in scan_control which is for
exporting scanning score.

Signed-off-by: KAMEZAWA Hiroyuki <[email protected]>
Cc: Daisuke Nishimura <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Ying Han <[email protected]>
Cc: Andrew Bresticker <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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hkamezawa authored and torvalds committed Jul 26, 2011
1 parent 108b6a7 commit 82f9d48
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85 changes: 84 additions & 1 deletion Documentation/cgroups/memory.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -380,7 +380,7 @@ will be charged as a new owner of it.

5.2 stat file

memory.stat file includes following statistics
5.2.1 memory.stat file includes following statistics

# per-memory cgroup local status
cache - # of bytes of page cache memory.
Expand Down Expand Up @@ -438,6 +438,89 @@ Note:
file_mapped is accounted only when the memory cgroup is owner of page
cache.)

5.2.2 memory.vmscan_stat

memory.vmscan_stat includes statistics information for memory scanning and
freeing, reclaiming. The statistics shows memory scanning information since
memory cgroup creation and can be reset to 0 by writing 0 as

#echo 0 > ../memory.vmscan_stat

This file contains following statistics.

[param]_[file_or_anon]_pages_by_[reason]_[under_heararchy]
[param]_elapsed_ns_by_[reason]_[under_hierarchy]

For example,

scanned_file_pages_by_limit indicates the number of scanned
file pages at vmscan.

Now, 3 parameters are supported

scanned - the number of pages scanned by vmscan
rotated - the number of pages activated at vmscan
freed - the number of pages freed by vmscan

If "rotated" is high against scanned/freed, the memcg seems busy.

Now, 2 reason are supported

limit - the memory cgroup's limit
system - global memory pressure + softlimit
(global memory pressure not under softlimit is not handled now)

When under_hierarchy is added in the tail, the number indicates the
total memcg scan of its children and itself.

elapsed_ns is a elapsed time in nanosecond. This may include sleep time
and not indicates CPU usage. So, please take this as just showing
latency.

Here is an example.

# cat /cgroup/memory/A/memory.vmscan_stat
scanned_pages_by_limit 9471864
scanned_anon_pages_by_limit 6640629
scanned_file_pages_by_limit 2831235
rotated_pages_by_limit 4243974
rotated_anon_pages_by_limit 3971968
rotated_file_pages_by_limit 272006
freed_pages_by_limit 2318492
freed_anon_pages_by_limit 962052
freed_file_pages_by_limit 1356440
elapsed_ns_by_limit 351386416101
scanned_pages_by_system 0
scanned_anon_pages_by_system 0
scanned_file_pages_by_system 0
rotated_pages_by_system 0
rotated_anon_pages_by_system 0
rotated_file_pages_by_system 0
freed_pages_by_system 0
freed_anon_pages_by_system 0
freed_file_pages_by_system 0
elapsed_ns_by_system 0
scanned_pages_by_limit_under_hierarchy 9471864
scanned_anon_pages_by_limit_under_hierarchy 6640629
scanned_file_pages_by_limit_under_hierarchy 2831235
rotated_pages_by_limit_under_hierarchy 4243974
rotated_anon_pages_by_limit_under_hierarchy 3971968
rotated_file_pages_by_limit_under_hierarchy 272006
freed_pages_by_limit_under_hierarchy 2318492
freed_anon_pages_by_limit_under_hierarchy 962052
freed_file_pages_by_limit_under_hierarchy 1356440
elapsed_ns_by_limit_under_hierarchy 351386416101
scanned_pages_by_system_under_hierarchy 0
scanned_anon_pages_by_system_under_hierarchy 0
scanned_file_pages_by_system_under_hierarchy 0
rotated_pages_by_system_under_hierarchy 0
rotated_anon_pages_by_system_under_hierarchy 0
rotated_file_pages_by_system_under_hierarchy 0
freed_pages_by_system_under_hierarchy 0
freed_anon_pages_by_system_under_hierarchy 0
freed_file_pages_by_system_under_hierarchy 0
elapsed_ns_by_system_under_hierarchy 0

5.3 swappiness

Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only.
Expand Down
19 changes: 19 additions & 0 deletions include/linux/memcontrol.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,16 @@ extern unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
struct mem_cgroup *mem_cont,
int active, int file);

struct memcg_scanrecord {
struct mem_cgroup *mem; /* scanend memory cgroup */
struct mem_cgroup *root; /* scan target hierarchy root */
int context; /* scanning context (see memcontrol.c) */
unsigned long nr_scanned[2]; /* the number of scanned pages */
unsigned long nr_rotated[2]; /* the number of rotated pages */
unsigned long nr_freed[2]; /* the number of freed pages */
unsigned long elapsed; /* nsec of time elapsed while scanning */
};

#ifdef CONFIG_CGROUP_MEM_RES_CTLR
/*
* All "charge" functions with gfp_mask should use GFP_KERNEL or
Expand Down Expand Up @@ -119,6 +129,15 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page);
extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
struct task_struct *p);

extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
gfp_t gfp_mask, bool noswap,
struct memcg_scanrecord *rec);
extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
gfp_t gfp_mask, bool noswap,
struct zone *zone,
struct memcg_scanrecord *rec,
unsigned long *nr_scanned);

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
extern int do_swap_account;
#endif
Expand Down
6 changes: 0 additions & 6 deletions include/linux/swap.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -251,12 +251,6 @@ static inline void lru_cache_add_file(struct page *page)
/* linux/mm/vmscan.c */
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);
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 int __isolate_lru_page(struct page *page, int mode, int file);
extern unsigned long shrink_all_memory(unsigned long nr_pages);
extern int vm_swappiness;
Expand Down
172 changes: 166 additions & 6 deletions mm/memcontrol.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -205,6 +205,50 @@ struct mem_cgroup_eventfd_list {
static void mem_cgroup_threshold(struct mem_cgroup *mem);
static void mem_cgroup_oom_notify(struct mem_cgroup *mem);

enum {
SCAN_BY_LIMIT,
SCAN_BY_SYSTEM,
NR_SCAN_CONTEXT,
SCAN_BY_SHRINK, /* not recorded now */
};

enum {
SCAN,
SCAN_ANON,
SCAN_FILE,
ROTATE,
ROTATE_ANON,
ROTATE_FILE,
FREED,
FREED_ANON,
FREED_FILE,
ELAPSED,
NR_SCANSTATS,
};

struct scanstat {
spinlock_t lock;
unsigned long stats[NR_SCAN_CONTEXT][NR_SCANSTATS];
unsigned long rootstats[NR_SCAN_CONTEXT][NR_SCANSTATS];
};

const char *scanstat_string[NR_SCANSTATS] = {
"scanned_pages",
"scanned_anon_pages",
"scanned_file_pages",
"rotated_pages",
"rotated_anon_pages",
"rotated_file_pages",
"freed_pages",
"freed_anon_pages",
"freed_file_pages",
"elapsed_ns",
};
#define SCANSTAT_WORD_LIMIT "_by_limit"
#define SCANSTAT_WORD_SYSTEM "_by_system"
#define SCANSTAT_WORD_HIERARCHY "_under_hierarchy"


/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
Expand Down Expand Up @@ -270,7 +314,8 @@ struct mem_cgroup {

/* For oom notifier event fd */
struct list_head oom_notify;

/* For recording LRU-scan statistics */
struct scanstat scanstat;
/*
* Should we move charges of a task when a task is moved into this
* mem_cgroup ? And what type of charges should we move ?
Expand Down Expand Up @@ -1623,6 +1668,44 @@ bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
}
#endif

static void __mem_cgroup_record_scanstat(unsigned long *stats,
struct memcg_scanrecord *rec)
{

stats[SCAN] += rec->nr_scanned[0] + rec->nr_scanned[1];
stats[SCAN_ANON] += rec->nr_scanned[0];
stats[SCAN_FILE] += rec->nr_scanned[1];

stats[ROTATE] += rec->nr_rotated[0] + rec->nr_rotated[1];
stats[ROTATE_ANON] += rec->nr_rotated[0];
stats[ROTATE_FILE] += rec->nr_rotated[1];

stats[FREED] += rec->nr_freed[0] + rec->nr_freed[1];
stats[FREED_ANON] += rec->nr_freed[0];
stats[FREED_FILE] += rec->nr_freed[1];

stats[ELAPSED] += rec->elapsed;
}

static void mem_cgroup_record_scanstat(struct memcg_scanrecord *rec)
{
struct mem_cgroup *mem;
int context = rec->context;

if (context >= NR_SCAN_CONTEXT)
return;

mem = rec->mem;
spin_lock(&mem->scanstat.lock);
__mem_cgroup_record_scanstat(mem->scanstat.stats[context], rec);
spin_unlock(&mem->scanstat.lock);

mem = rec->root;
spin_lock(&mem->scanstat.lock);
__mem_cgroup_record_scanstat(mem->scanstat.rootstats[context], rec);
spin_unlock(&mem->scanstat.lock);
}

/*
* Scan the hierarchy if needed to reclaim memory. We remember the last child
* we reclaimed from, so that we don't end up penalizing one child extensively
Expand All @@ -1647,15 +1730,25 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
bool noswap = reclaim_options & MEM_CGROUP_RECLAIM_NOSWAP;
bool shrink = reclaim_options & MEM_CGROUP_RECLAIM_SHRINK;
bool check_soft = reclaim_options & MEM_CGROUP_RECLAIM_SOFT;
struct memcg_scanrecord rec;
unsigned long excess;
unsigned long nr_scanned;
unsigned long scanned;

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

/* If memsw_is_minimum==1, swap-out is of-no-use. */
if (!check_soft && !shrink && root_mem->memsw_is_minimum)
noswap = true;

if (shrink)
rec.context = SCAN_BY_SHRINK;
else if (check_soft)
rec.context = SCAN_BY_SYSTEM;
else
rec.context = SCAN_BY_LIMIT;

rec.root = root_mem;

while (1) {
victim = mem_cgroup_select_victim(root_mem);
if (victim == root_mem) {
Expand Down Expand Up @@ -1696,14 +1789,23 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
css_put(&victim->css);
continue;
}
rec.mem = victim;
rec.nr_scanned[0] = 0;
rec.nr_scanned[1] = 0;
rec.nr_rotated[0] = 0;
rec.nr_rotated[1] = 0;
rec.nr_freed[0] = 0;
rec.nr_freed[1] = 0;
rec.elapsed = 0;
/* we use swappiness of local cgroup */
if (check_soft) {
ret = mem_cgroup_shrink_node_zone(victim, gfp_mask,
noswap, zone, &nr_scanned);
*total_scanned += nr_scanned;
noswap, zone, &rec, &scanned);
*total_scanned += scanned;
} else
ret = try_to_free_mem_cgroup_pages(victim, gfp_mask,
noswap);
noswap, &rec);
mem_cgroup_record_scanstat(&rec);
css_put(&victim->css);
/*
* At shrinking usage, we can't check we should stop here or
Expand Down Expand Up @@ -3792,14 +3894,18 @@ static int mem_cgroup_force_empty(struct mem_cgroup *mem, bool free_all)
/* try to free all pages in this cgroup */
shrink = 1;
while (nr_retries && mem->res.usage > 0) {
struct memcg_scanrecord rec;
int progress;

if (signal_pending(current)) {
ret = -EINTR;
goto out;
}
rec.context = SCAN_BY_SHRINK;
rec.mem = mem;
rec.root = mem;
progress = try_to_free_mem_cgroup_pages(mem, GFP_KERNEL,
false);
false, &rec);
if (!progress) {
nr_retries--;
/* maybe some writeback is necessary */
Expand Down Expand Up @@ -4643,6 +4749,54 @@ static int mem_control_numa_stat_open(struct inode *unused, struct file *file)
}
#endif /* CONFIG_NUMA */

static int mem_cgroup_vmscan_stat_read(struct cgroup *cgrp,
struct cftype *cft,
struct cgroup_map_cb *cb)
{
struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);
char string[64];
int i;

for (i = 0; i < NR_SCANSTATS; i++) {
strcpy(string, scanstat_string[i]);
strcat(string, SCANSTAT_WORD_LIMIT);
cb->fill(cb, string, mem->scanstat.stats[SCAN_BY_LIMIT][i]);
}

for (i = 0; i < NR_SCANSTATS; i++) {
strcpy(string, scanstat_string[i]);
strcat(string, SCANSTAT_WORD_SYSTEM);
cb->fill(cb, string, mem->scanstat.stats[SCAN_BY_SYSTEM][i]);
}

for (i = 0; i < NR_SCANSTATS; i++) {
strcpy(string, scanstat_string[i]);
strcat(string, SCANSTAT_WORD_LIMIT);
strcat(string, SCANSTAT_WORD_HIERARCHY);
cb->fill(cb, string, mem->scanstat.rootstats[SCAN_BY_LIMIT][i]);
}
for (i = 0; i < NR_SCANSTATS; i++) {
strcpy(string, scanstat_string[i]);
strcat(string, SCANSTAT_WORD_SYSTEM);
strcat(string, SCANSTAT_WORD_HIERARCHY);
cb->fill(cb, string, mem->scanstat.rootstats[SCAN_BY_SYSTEM][i]);
}
return 0;
}

static int mem_cgroup_reset_vmscan_stat(struct cgroup *cgrp,
unsigned int event)
{
struct mem_cgroup *mem = mem_cgroup_from_cont(cgrp);

spin_lock(&mem->scanstat.lock);
memset(&mem->scanstat.stats, 0, sizeof(mem->scanstat.stats));
memset(&mem->scanstat.rootstats, 0, sizeof(mem->scanstat.rootstats));
spin_unlock(&mem->scanstat.lock);
return 0;
}


static struct cftype mem_cgroup_files[] = {
{
.name = "usage_in_bytes",
Expand Down Expand Up @@ -4713,6 +4867,11 @@ static struct cftype mem_cgroup_files[] = {
.mode = S_IRUGO,
},
#endif
{
.name = "vmscan_stat",
.read_map = mem_cgroup_vmscan_stat_read,
.trigger = mem_cgroup_reset_vmscan_stat,
},
};

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
Expand Down Expand Up @@ -4976,6 +5135,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
atomic_set(&mem->refcnt, 1);
mem->move_charge_at_immigrate = 0;
mutex_init(&mem->thresholds_lock);
spin_lock_init(&mem->scanstat.lock);
return &mem->css;
free_out:
__mem_cgroup_free(mem);
Expand Down
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