memcg: add memory.vmscan_stat

The commit log of 0ae5e89c60c9 ("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 <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Ying Han <yinghan@google.com>
Cc: Andrew Bresticker <abrestic@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 200 insertions, 11 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index dfeca594fd7a..04e505bfd7dd 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -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
@@ -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 ?
@@ -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
@@ -1647,8 +1730,9 @@ 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;
 
@@ -1656,6 +1740,15 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
         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) {
@@ -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
@@ -3792,14 +3894,18 @@ try_to_free:
         /* 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 */
@@ -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",
@@ -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
@@ -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);
diff --git a/mm/vmscan.c b/mm/vmscan.c
index f87702a376d0..7ef69124fa3e 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -105,6 +105,7 @@ struct scan_control {
 
         /* Which cgroup do we reclaim from */
         struct mem_cgroup *mem_cgroup;
+        struct memcg_scanrecord *memcg_record;
 
         /*
          * Nodemask of nodes allowed by the caller. If NULL, all nodes
@@ -1348,6 +1349,8 @@ putback_lru_pages(struct zone *zone, struct scan_control *sc,
                         int file = is_file_lru(lru);
                         int numpages = hpage_nr_pages(page);
                         reclaim_stat->recent_rotated[file] += numpages;
+                        if (!scanning_global_lru(sc))
+                                sc->memcg_record->nr_rotated[file] += numpages;
                 }
                 if (!pagevec_add(&pvec, page)) {
                         spin_unlock_irq(&zone->lru_lock);
@@ -1391,6 +1394,10 @@ static noinline_for_stack void update_isolated_counts(struct zone *zone,
 
         reclaim_stat->recent_scanned[0] += *nr_anon;
         reclaim_stat->recent_scanned[1] += *nr_file;
+        if (!scanning_global_lru(sc)) {
+                sc->memcg_record->nr_scanned[0] += *nr_anon;
+                sc->memcg_record->nr_scanned[1] += *nr_file;
+        }
 }
 
 /*
@@ -1504,6 +1511,9 @@ shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone,
                 nr_reclaimed += shrink_page_list(&page_list, zone, sc);
         }
 
+        if (!scanning_global_lru(sc))
+                sc->memcg_record->nr_freed[file] += nr_reclaimed;
+
         local_irq_disable();
         if (current_is_kswapd())
                 __count_vm_events(KSWAPD_STEAL, nr_reclaimed);
@@ -1603,6 +1613,8 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
         }
 
         reclaim_stat->recent_scanned[file] += nr_taken;
+        if (!scanning_global_lru(sc))
+                sc->memcg_record->nr_scanned[file] += nr_taken;
 
         __count_zone_vm_events(PGREFILL, zone, pgscanned);
         if (file)
@@ -1654,6 +1666,8 @@ static void shrink_active_list(unsigned long nr_pages, struct zone *zone,
          * get_scan_ratio.
          */
         reclaim_stat->recent_rotated[file] += nr_rotated;
+        if (!scanning_global_lru(sc))
+                sc->memcg_record->nr_rotated[file] += nr_rotated;
 
         move_active_pages_to_lru(zone, &l_active,
                                                 LRU_ACTIVE + file * LRU_FILE);
@@ -2254,9 +2268,10 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR
 
 unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
-                                                gfp_t gfp_mask, bool noswap,
-                                                struct zone *zone,
-                                                unsigned long *nr_scanned)
+                                        gfp_t gfp_mask, bool noswap,
+                                        struct zone *zone,
+                                        struct memcg_scanrecord *rec,
+                                        unsigned long *scanned)
 {
         struct scan_control sc = {
                 .nr_scanned = 0,
@@ -2266,7 +2281,9 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
                 .may_swap = !noswap,
                 .order = 0,
                 .mem_cgroup = mem,
+                .memcg_record = rec,
         };
+        unsigned long start, end;
 
         sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
                         (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK);
@@ -2275,6 +2292,7 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
                                                       sc.may_writepage,
                                                       sc.gfp_mask);
 
+        start = sched_clock();
         /*
          * NOTE: Although we can get the priority field, using it
          * here is not a good idea, since it limits the pages we can scan.
@@ -2283,19 +2301,25 @@ unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
          * the priority and make it zero.
          */
         shrink_zone(0, zone, &sc);
+        end = sched_clock();
+
+        if (rec)
+                rec->elapsed += end - start;
+        *scanned = sc.nr_scanned;
 
         trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed);
 
-        *nr_scanned = sc.nr_scanned;
         return sc.nr_reclaimed;
 }
 
 unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
                                            gfp_t gfp_mask,
-                                           bool noswap)
+                                           bool noswap,
+                                           struct memcg_scanrecord *rec)
 {
         struct zonelist *zonelist;
         unsigned long nr_reclaimed;
+        unsigned long start, end;
         int nid;
         struct scan_control sc = {
                 .may_writepage = !laptop_mode,
@@ -2304,6 +2328,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
                 .nr_to_reclaim = SWAP_CLUSTER_MAX,
                 .order = 0,
                 .mem_cgroup = mem_cont,
+                .memcg_record = rec,
                 .nodemask = NULL, /* we don't care the placement */
                 .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) |
                                 (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK),
@@ -2312,6 +2337,7 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
                 .gfp_mask = sc.gfp_mask,
         };
 
+        start = sched_clock();
         /*
          * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't
          * take care of from where we get pages. So the node where we start the
@@ -2326,6 +2352,9 @@ unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont,
                                             sc.gfp_mask);
 
         nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink);
+        end = sched_clock();
+        if (rec)
+                rec->elapsed += end - start;
 
         trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed);