memory controller: soft limit organize cgroups

Organize cgroups over soft limit in a RB-Tree

Introduce an RB-Tree for storing memory cgroups that are over their soft
limit.  The overall goal is to

1. Add a memory cgroup to the RB-Tree when the soft limit is exceeded.
   We are careful about updates, updates take place only after a particular
   time interval has passed
2. We remove the node from the RB-Tree when the usage goes below the soft
   limit

The next set of patches will exploit the RB-Tree to get the group that is
over its soft limit by the largest amount and reclaim from it, when we
face memory contention.

[hugh.dickins@tiscali.co.uk: CONFIG_CGROUP_MEM_RES_CTLR=y CONFIG_PREEMPT=y fails to boot]
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 257 insertions, 43 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 4ad3e6be045d..0ed325943cd1 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -29,6 +29,7 @@
 #include <linux/rcupdate.h>
 #include <linux/limits.h>
 #include <linux/mutex.h>
+#include <linux/rbtree.h>
 #include <linux/slab.h>
 #include <linux/swap.h>
 #include <linux/spinlock.h>
@@ -54,6 +55,7 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
 #endif
 
 static DEFINE_MUTEX(memcg_tasklist);    /* can be hold under cgroup_mutex */
+#define SOFTLIMIT_EVENTS_THRESH (1000)
 
 /*
  * Statistics for memory cgroup.
@@ -67,6 +69,7 @@ enum mem_cgroup_stat_index {
         MEM_CGROUP_STAT_MAPPED_FILE,  /* # of pages charged as file rss */
         MEM_CGROUP_STAT_PGPGIN_COUNT,   /* # of pages paged in */
         MEM_CGROUP_STAT_PGPGOUT_COUNT,  /* # of pages paged out */
+        MEM_CGROUP_STAT_EVENTS, /* sum of pagein + pageout for internal use */
 
         MEM_CGROUP_STAT_NSTATS,
 };
@@ -79,6 +82,20 @@ struct mem_cgroup_stat {
         struct mem_cgroup_stat_cpu cpustat[0];
 };
 
+static inline void
+__mem_cgroup_stat_reset_safe(struct mem_cgroup_stat_cpu *stat,
+                                enum mem_cgroup_stat_index idx)
+{
+        stat->count[idx] = 0;
+}
+
+static inline s64
+__mem_cgroup_stat_read_local(struct mem_cgroup_stat_cpu *stat,
+                                enum mem_cgroup_stat_index idx)
+{
+        return stat->count[idx];
+}
+
 /*
  * For accounting under irq disable, no need for increment preempt count.
  */
@@ -118,6 +135,10 @@ struct mem_cgroup_per_zone {
         unsigned long           count[NR_LRU_LISTS];
 
         struct zone_reclaim_stat reclaim_stat;
+        struct rb_node          tree_node;      /* RB tree node */
+        unsigned long long      usage_in_excess;/* Set to the value by which */
+                                                /* the soft limit is exceeded*/
+        bool                    on_tree;
 };
 /* Macro for accessing counter */
 #define MEM_CGROUP_ZSTAT(mz, idx)       ((mz)->count[(idx)])
@@ -131,6 +152,26 @@ struct mem_cgroup_lru_info {
 };
 
 /*
+ * Cgroups above their limits are maintained in a RB-Tree, independent of
+ * their hierarchy representation
+ */
+
+struct mem_cgroup_tree_per_zone {
+        struct rb_root rb_root;
+        spinlock_t lock;
+};
+
+struct mem_cgroup_tree_per_node {
+        struct mem_cgroup_tree_per_zone rb_tree_per_zone[MAX_NR_ZONES];
+};
+
+struct mem_cgroup_tree {
+        struct mem_cgroup_tree_per_node *rb_tree_per_node[MAX_NUMNODES];
+};
+
+static struct mem_cgroup_tree soft_limit_tree __read_mostly;
+
+/*
  * The memory controller data structure. The memory controller controls both
  * page cache and RSS per cgroup. We would eventually like to provide
  * statistics based on the statistics developed by Rik Van Riel for clock-pro,
@@ -215,6 +256,150 @@ static void mem_cgroup_get(struct mem_cgroup *mem);
 static void mem_cgroup_put(struct mem_cgroup *mem);
 static struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *mem);
 
+static struct mem_cgroup_per_zone *
+mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
+{
+        return &mem->info.nodeinfo[nid]->zoneinfo[zid];
+}
+
+static struct mem_cgroup_per_zone *
+page_cgroup_zoneinfo(struct page_cgroup *pc)
+{
+        struct mem_cgroup *mem = pc->mem_cgroup;
+        int nid = page_cgroup_nid(pc);
+        int zid = page_cgroup_zid(pc);
+
+        if (!mem)
+                return NULL;
+
+        return mem_cgroup_zoneinfo(mem, nid, zid);
+}
+
+static struct mem_cgroup_tree_per_zone *
+soft_limit_tree_node_zone(int nid, int zid)
+{
+        return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
+}
+
+static struct mem_cgroup_tree_per_zone *
+soft_limit_tree_from_page(struct page *page)
+{
+        int nid = page_to_nid(page);
+        int zid = page_zonenum(page);
+
+        return &soft_limit_tree.rb_tree_per_node[nid]->rb_tree_per_zone[zid];
+}
+
+static void
+mem_cgroup_insert_exceeded(struct mem_cgroup *mem,
+                                struct mem_cgroup_per_zone *mz,
+                                struct mem_cgroup_tree_per_zone *mctz)
+{
+        struct rb_node **p = &mctz->rb_root.rb_node;
+        struct rb_node *parent = NULL;
+        struct mem_cgroup_per_zone *mz_node;
+
+        if (mz->on_tree)
+                return;
+
+        mz->usage_in_excess = res_counter_soft_limit_excess(&mem->res);
+        spin_lock(&mctz->lock);
+        while (*p) {
+                parent = *p;
+                mz_node = rb_entry(parent, struct mem_cgroup_per_zone,
+                                        tree_node);
+                if (mz->usage_in_excess < mz_node->usage_in_excess)
+                        p = &(*p)->rb_left;
+                /*
+                 * We can't avoid mem cgroups that are over their soft
+                 * limit by the same amount
+                 */
+                else if (mz->usage_in_excess >= mz_node->usage_in_excess)
+                        p = &(*p)->rb_right;
+        }
+        rb_link_node(&mz->tree_node, parent, p);
+        rb_insert_color(&mz->tree_node, &mctz->rb_root);
+        mz->on_tree = true;
+        spin_unlock(&mctz->lock);
+}
+
+static void
+mem_cgroup_remove_exceeded(struct mem_cgroup *mem,
+                                struct mem_cgroup_per_zone *mz,
+                                struct mem_cgroup_tree_per_zone *mctz)
+{
+        spin_lock(&mctz->lock);
+        rb_erase(&mz->tree_node, &mctz->rb_root);
+        mz->on_tree = false;
+        spin_unlock(&mctz->lock);
+}
+
+static bool mem_cgroup_soft_limit_check(struct mem_cgroup *mem)
+{
+        bool ret = false;
+        int cpu;
+        s64 val;
+        struct mem_cgroup_stat_cpu *cpustat;
+
+        cpu = get_cpu();
+        cpustat = &mem->stat.cpustat[cpu];
+        val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_EVENTS);
+        if (unlikely(val > SOFTLIMIT_EVENTS_THRESH)) {
+                __mem_cgroup_stat_reset_safe(cpustat, MEM_CGROUP_STAT_EVENTS);
+                ret = true;
+        }
+        put_cpu();
+        return ret;
+}
+
+static void mem_cgroup_update_tree(struct mem_cgroup *mem, struct page *page)
+{
+        unsigned long long prev_usage_in_excess, new_usage_in_excess;
+        bool updated_tree = false;
+        struct mem_cgroup_per_zone *mz;
+        struct mem_cgroup_tree_per_zone *mctz;
+
+        mz = mem_cgroup_zoneinfo(mem, page_to_nid(page), page_zonenum(page));
+        mctz = soft_limit_tree_from_page(page);
+
+        /*
+         * We do updates in lazy mode, mem's are removed
+         * lazily from the per-zone, per-node rb tree
+         */
+        prev_usage_in_excess = mz->usage_in_excess;
+
+        new_usage_in_excess = res_counter_soft_limit_excess(&mem->res);
+        if (prev_usage_in_excess) {
+                mem_cgroup_remove_exceeded(mem, mz, mctz);
+                updated_tree = true;
+        }
+        if (!new_usage_in_excess)
+                goto done;
+        mem_cgroup_insert_exceeded(mem, mz, mctz);
+
+done:
+        if (updated_tree) {
+                spin_lock(&mctz->lock);
+                mz->usage_in_excess = new_usage_in_excess;
+                spin_unlock(&mctz->lock);
+        }
+}
+
+static void mem_cgroup_remove_from_trees(struct mem_cgroup *mem)
+{
+        int node, zone;
+        struct mem_cgroup_per_zone *mz;
+        struct mem_cgroup_tree_per_zone *mctz;
+
+        for_each_node_state(node, N_POSSIBLE) {
+                for (zone = 0; zone < MAX_NR_ZONES; zone++) {
+                        mz = mem_cgroup_zoneinfo(mem, node, zone);
+                        mctz = soft_limit_tree_node_zone(node, zone);
+                        mem_cgroup_remove_exceeded(mem, mz, mctz);
+                }
+        }
+}
+
 static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
                                          struct page_cgroup *pc,
                                          bool charge)
@@ -236,28 +421,10 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
         else
                 __mem_cgroup_stat_add_safe(cpustat,
                                 MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
+        __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_EVENTS, 1);
         put_cpu();
 }
 
-static struct mem_cgroup_per_zone *
-mem_cgroup_zoneinfo(struct mem_cgroup *mem, int nid, int zid)
-{
-        return &mem->info.nodeinfo[nid]->zoneinfo[zid];
-}
-
-static struct mem_cgroup_per_zone *
-page_cgroup_zoneinfo(struct page_cgroup *pc)
-{
-        struct mem_cgroup *mem = pc->mem_cgroup;
-        int nid = page_cgroup_nid(pc);
-        int zid = page_cgroup_zid(pc);
-
-        if (!mem)
-                return NULL;
-
-        return mem_cgroup_zoneinfo(mem, nid, zid);
-}
-
 static unsigned long mem_cgroup_get_local_zonestat(struct mem_cgroup *mem,
                                         enum lru_list idx)
 {
@@ -972,11 +1139,11 @@ done:
  */
 static int __mem_cgroup_try_charge(struct mm_struct *mm,
                         gfp_t gfp_mask, struct mem_cgroup **memcg,
-                        bool oom)
+                        bool oom, struct page *page)
 {
-        struct mem_cgroup *mem, *mem_over_limit;
+        struct mem_cgroup *mem, *mem_over_limit, *mem_over_soft_limit;
         int nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
-        struct res_counter *fail_res;
+        struct res_counter *fail_res, *soft_fail_res = NULL;
 
         if (unlikely(test_thread_flag(TIF_MEMDIE))) {
                 /* Don't account this! */
@@ -1006,16 +1173,17 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
                 int ret;
                 bool noswap = false;
 
-                ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res);
+                ret = res_counter_charge(&mem->res, PAGE_SIZE, &fail_res,
+                                                &soft_fail_res);
                 if (likely(!ret)) {
                         if (!do_swap_account)
                                 break;
                         ret = res_counter_charge(&mem->memsw, PAGE_SIZE,
-                                                        &fail_res);
+                                                        &fail_res, NULL);
                         if (likely(!ret))
                                 break;
                         /* mem+swap counter fails */
-                        res_counter_uncharge(&mem->res, PAGE_SIZE);
+                        res_counter_uncharge(&mem->res, PAGE_SIZE, NULL);
                         noswap = true;
                         mem_over_limit = mem_cgroup_from_res_counter(fail_res,
                                                                         memsw);
@@ -1053,13 +1221,23 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm,
                         goto nomem;
                 }
         }
+        /*
+         * Insert just the ancestor, we should trickle down to the correct
+         * cgroup for reclaim, since the other nodes will be below their
+         * soft limit
+         */
+        if (soft_fail_res) {
+                mem_over_soft_limit =
+                        mem_cgroup_from_res_counter(soft_fail_res, res);
+                if (mem_cgroup_soft_limit_check(mem_over_soft_limit))
+                        mem_cgroup_update_tree(mem_over_soft_limit, page);
+        }
         return 0;
 nomem:
         css_put(&mem->css);
         return -ENOMEM;
 }
 
-
 /*
  * A helper function to get mem_cgroup from ID. must be called under
  * rcu_read_lock(). The caller must check css_is_removed() or some if
@@ -1126,9 +1304,9 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
         lock_page_cgroup(pc);
         if (unlikely(PageCgroupUsed(pc))) {
                 unlock_page_cgroup(pc);
-                res_counter_uncharge(&mem->res, PAGE_SIZE);
+                res_counter_uncharge(&mem->res, PAGE_SIZE, NULL);
                 if (do_swap_account)
-                        res_counter_uncharge(&mem->memsw, PAGE_SIZE);
+                        res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
                 css_put(&mem->css);
                 return;
         }
@@ -1205,7 +1383,7 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
         if (pc->mem_cgroup != from)
                 goto out;
 
-        res_counter_uncharge(&from->res, PAGE_SIZE);
+        res_counter_uncharge(&from->res, PAGE_SIZE, NULL);
         mem_cgroup_charge_statistics(from, pc, false);
 
         page = pc->page;
@@ -1225,7 +1403,7 @@ static int mem_cgroup_move_account(struct page_cgroup *pc,
         }
 
         if (do_swap_account)
-                res_counter_uncharge(&from->memsw, PAGE_SIZE);
+                res_counter_uncharge(&from->memsw, PAGE_SIZE, NULL);
         css_put(&from->css);
 
         css_get(&to->css);
@@ -1265,7 +1443,7 @@ static int mem_cgroup_move_parent(struct page_cgroup *pc,
         parent = mem_cgroup_from_cont(pcg);
 
 
-        ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false);
+        ret = __mem_cgroup_try_charge(NULL, gfp_mask, &parent, false, page);
         if (ret || !parent)
                 return ret;
 
@@ -1295,9 +1473,9 @@ uncharge:
         /* drop extra refcnt by try_charge() */
         css_put(&parent->css);
         /* uncharge if move fails */
-        res_counter_uncharge(&parent->res, PAGE_SIZE);
+        res_counter_uncharge(&parent->res, PAGE_SIZE, NULL);
         if (do_swap_account)
-                res_counter_uncharge(&parent->memsw, PAGE_SIZE);
+                res_counter_uncharge(&parent->memsw, PAGE_SIZE, NULL);
         return ret;
 }
 
@@ -1322,7 +1500,7 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
         prefetchw(pc);
 
         mem = memcg;
-        ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, true);
+        ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, true, page);
         if (ret || !mem)
                 return ret;
 
@@ -1441,14 +1619,14 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm,
         if (!mem)
                 goto charge_cur_mm;
         *ptr = mem;
-        ret = __mem_cgroup_try_charge(NULL, mask, ptr, true);
+        ret = __mem_cgroup_try_charge(NULL, mask, ptr, true, page);
         /* drop extra refcnt from tryget */
         css_put(&mem->css);
         return ret;
 charge_cur_mm:
         if (unlikely(!mm))
                 mm = &init_mm;
-        return __mem_cgroup_try_charge(mm, mask, ptr, true);
+        return __mem_cgroup_try_charge(mm, mask, ptr, true, page);
 }
 
 static void
@@ -1486,7 +1664,7 @@ __mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr,
                          * This recorded memcg can be obsolete one. So, avoid
                          * calling css_tryget
                          */
-                        res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
+                        res_counter_uncharge(&memcg->memsw, PAGE_SIZE, NULL);
                         mem_cgroup_put(memcg);
                 }
                 rcu_read_unlock();
@@ -1511,9 +1689,9 @@ void mem_cgroup_cancel_charge_swapin(struct mem_cgroup *mem)
                 return;
         if (!mem)
                 return;
-        res_counter_uncharge(&mem->res, PAGE_SIZE);
+        res_counter_uncharge(&mem->res, PAGE_SIZE, NULL);
         if (do_swap_account)
-                res_counter_uncharge(&mem->memsw, PAGE_SIZE);
+                res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
         css_put(&mem->css);
 }
 
@@ -1527,6 +1705,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
         struct page_cgroup *pc;
         struct mem_cgroup *mem = NULL;
         struct mem_cgroup_per_zone *mz;
+        bool soft_limit_excess = false;
 
         if (mem_cgroup_disabled())
                 return NULL;
@@ -1565,9 +1744,9 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
                 break;
         }
 
-        res_counter_uncharge(&mem->res, PAGE_SIZE);
+        res_counter_uncharge(&mem->res, PAGE_SIZE, &soft_limit_excess);
         if (do_swap_account && (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT))
-                res_counter_uncharge(&mem->memsw, PAGE_SIZE);
+                res_counter_uncharge(&mem->memsw, PAGE_SIZE, NULL);
         mem_cgroup_charge_statistics(mem, pc, false);
 
         ClearPageCgroupUsed(pc);
@@ -1581,6 +1760,8 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
         mz = page_cgroup_zoneinfo(pc);
         unlock_page_cgroup(pc);
 
+        if (soft_limit_excess && mem_cgroup_soft_limit_check(mem))
+                mem_cgroup_update_tree(mem, page);
         /* at swapout, this memcg will be accessed to record to swap */
         if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
                 css_put(&mem->css);
@@ -1656,7 +1837,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent)
                  * We uncharge this because swap is freed.
                  * This memcg can be obsolete one. We avoid calling css_tryget
                  */
-                res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
+                res_counter_uncharge(&memcg->memsw, PAGE_SIZE, NULL);
                 mem_cgroup_put(memcg);
         }
         rcu_read_unlock();
@@ -1685,7 +1866,8 @@ int mem_cgroup_prepare_migration(struct page *page, struct mem_cgroup **ptr)
         unlock_page_cgroup(pc);
 
         if (mem) {
-                ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem, false);
+                ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem, false,
+                                                page);
                 css_put(&mem->css);
         }
         *ptr = mem;
@@ -2194,6 +2376,7 @@ static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
                         res_counter_reset_failcnt(&mem->memsw);
                 break;
         }
+
         return 0;
 }
 
@@ -2489,6 +2672,7 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
                 mz = &pn->zoneinfo[zone];
                 for_each_lru(l)
                         INIT_LIST_HEAD(&mz->lists[l]);
+                mz->usage_in_excess = 0;
         }
         return 0;
 }
@@ -2534,6 +2718,7 @@ static void __mem_cgroup_free(struct mem_cgroup *mem)
 {
         int node;
 
+        mem_cgroup_remove_from_trees(mem);
         free_css_id(&mem_cgroup_subsys, &mem->css);
 
         for_each_node_state(node, N_POSSIBLE)
@@ -2582,6 +2767,31 @@ static void __init enable_swap_cgroup(void)
 }
 #endif
 
+static int mem_cgroup_soft_limit_tree_init(void)
+{
+        struct mem_cgroup_tree_per_node *rtpn;
+        struct mem_cgroup_tree_per_zone *rtpz;
+        int tmp, node, zone;
+
+        for_each_node_state(node, N_POSSIBLE) {
+                tmp = node;
+                if (!node_state(node, N_NORMAL_MEMORY))
+                        tmp = -1;
+                rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp);
+                if (!rtpn)
+                        return 1;
+
+                soft_limit_tree.rb_tree_per_node[node] = rtpn;
+
+                for (zone = 0; zone < MAX_NR_ZONES; zone++) {
+                        rtpz = &rtpn->rb_tree_per_zone[zone];
+                        rtpz->rb_root = RB_ROOT;
+                        spin_lock_init(&rtpz->lock);
+                }
+        }
+        return 0;
+}
+
 static struct cgroup_subsys_state * __ref
 mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 {
@@ -2596,11 +2806,15 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
         for_each_node_state(node, N_POSSIBLE)
                 if (alloc_mem_cgroup_per_zone_info(mem, node))
                         goto free_out;
+
         /* root ? */
         if (cont->parent == NULL) {
                 enable_swap_cgroup();
                 parent = NULL;
                 root_mem_cgroup = mem;
+                if (mem_cgroup_soft_limit_tree_init())
+                        goto free_out;
+
         } else {
                 parent = mem_cgroup_from_cont(cont->parent);
                 mem->use_hierarchy = parent->use_hierarchy;