memcg: remove the overhead associated with the root cgroup

[net-next-2.6.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index cf2e717f5c1294b43b6d016e60f08f7ad2ff46bd..b0757660663f47e570208abd18182c44c4e47798 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -43,6 +43,7 @@
 
 struct cgroup_subsys mem_cgroup_subsys __read_mostly;
 #define MEM_CGROUP_RECLAIM_RETRIES     5
+struct mem_cgroup *root_mem_cgroup __read_mostly;
 
 #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
 /* Turned on only when memory cgroup is enabled && really_do_swap_account = 1 */
@@ -200,13 +201,8 @@ enum charge_type {
 #define PCGF_CACHE     (1UL << PCG_CACHE)
 #define PCGF_USED      (1UL << PCG_USED)
 #define PCGF_LOCK      (1UL << PCG_LOCK)
-static const unsigned long
-pcg_default_flags[NR_CHARGE_TYPE] = {
-       PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* File Cache */
-       PCGF_USED | PCGF_LOCK, /* Anon */
-       PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* Shmem */
-       0, /* FORCE */
-};
+/* Not used, but added here for completeness */
+#define PCGF_ACCT      (1UL << PCG_ACCT)
 
 /* for encoding cft->private value on file */
 #define _MEM                   (0)
@@ -354,6 +350,11 @@ static int mem_cgroup_walk_tree(struct mem_cgroup *root, void *data,
        return ret;
 }
 
+static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
+{
+       return (mem == root_mem_cgroup);
+}
+
 /*
  * Following LRU functions are allowed to be used without PCG_LOCK.
  * Operations are called by routine of global LRU independently from memcg.
@@ -371,22 +372,24 @@ static int mem_cgroup_walk_tree(struct mem_cgroup *root, void *data,
 void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru)
 {
        struct page_cgroup *pc;
-       struct mem_cgroup *mem;
        struct mem_cgroup_per_zone *mz;
 
        if (mem_cgroup_disabled())
                return;
        pc = lookup_page_cgroup(page);
        /* can happen while we handle swapcache. */
-       if (list_empty(&pc->lru) || !pc->mem_cgroup)
+       if (!TestClearPageCgroupAcctLRU(pc))
                return;
+       VM_BUG_ON(!pc->mem_cgroup);
        /*
         * We don't check PCG_USED bit. It's cleared when the "page" is finally
         * removed from global LRU.
         */
        mz = page_cgroup_zoneinfo(pc);
-       mem = pc->mem_cgroup;
        MEM_CGROUP_ZSTAT(mz, lru) -= 1;
+       if (mem_cgroup_is_root(pc->mem_cgroup))
+               return;
+       VM_BUG_ON(list_empty(&pc->lru));
        list_del_init(&pc->lru);
        return;
 }
@@ -410,8 +413,8 @@ void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
         * For making pc->mem_cgroup visible, insert smp_rmb() here.
         */
        smp_rmb();
-       /* unused page is not rotated. */
-       if (!PageCgroupUsed(pc))
+       /* unused or root page is not rotated. */
+       if (!PageCgroupUsed(pc) || mem_cgroup_is_root(pc->mem_cgroup))
                return;
        mz = page_cgroup_zoneinfo(pc);
        list_move(&pc->lru, &mz->lists[lru]);
@@ -425,6 +428,7 @@ void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
        if (mem_cgroup_disabled())
                return;
        pc = lookup_page_cgroup(page);
+       VM_BUG_ON(PageCgroupAcctLRU(pc));
        /*
         * Used bit is set without atomic ops but after smp_wmb().
         * For making pc->mem_cgroup visible, insert smp_rmb() here.
@@ -435,6 +439,9 @@ void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru)
 
        mz = page_cgroup_zoneinfo(pc);
        MEM_CGROUP_ZSTAT(mz, lru) += 1;
+       SetPageCgroupAcctLRU(pc);
+       if (mem_cgroup_is_root(pc->mem_cgroup))
+               return;
        list_add(&pc->lru, &mz->lists[lru]);
 }
 
@@ -469,7 +476,7 @@ static void mem_cgroup_lru_add_after_commit_swapcache(struct page *page)
 
        spin_lock_irqsave(&zone->lru_lock, flags);
        /* link when the page is linked to LRU but page_cgroup isn't */
-       if (PageLRU(page) && list_empty(&pc->lru))
+       if (PageLRU(page) && !PageCgroupAcctLRU(pc))
                mem_cgroup_add_lru_list(page, page_lru(page));
        spin_unlock_irqrestore(&zone->lru_lock, flags);
 }
@@ -1125,9 +1132,22 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *mem,
                css_put(&mem->css);
                return;
        }
+
        pc->mem_cgroup = mem;
        smp_wmb();
-       pc->flags = pcg_default_flags[ctype];
+       switch (ctype) {
+       case MEM_CGROUP_CHARGE_TYPE_CACHE:
+       case MEM_CGROUP_CHARGE_TYPE_SHMEM:
+               SetPageCgroupCache(pc);
+               SetPageCgroupUsed(pc);
+               break;
+       case MEM_CGROUP_CHARGE_TYPE_MAPPED:
+               ClearPageCgroupCache(pc);
+               SetPageCgroupUsed(pc);
+               break;
+       default:
+               break;
+       }
 
        mem_cgroup_charge_statistics(mem, pc, true);
 
@@ -2083,6 +2103,10 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
        name = MEMFILE_ATTR(cft->private);
        switch (name) {
        case RES_LIMIT:
+               if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
+                       ret = -EINVAL;
+                       break;
+               }
                /* This function does all necessary parse...reuse it */
                ret = res_counter_memparse_write_strategy(buffer, &val);
                if (ret)
@@ -2549,6 +2573,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
        if (cont->parent == NULL) {
                enable_swap_cgroup();
                parent = NULL;
+               root_mem_cgroup = mem;
        } else {
                parent = mem_cgroup_from_cont(cont->parent);
                mem->use_hierarchy = parent->use_hierarchy;
@@ -2577,6 +2602,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
        return &mem->css;
 free_out:
        __mem_cgroup_free(mem);
+       root_mem_cgroup = NULL;
        return ERR_PTR(error);
 }