[PATCH v5 2/8] memcg: Get rid of soft-limit tree infrastructure

From: Michal Hocko
Date: Tue Jun 18 2013 - 08:11:17 EST


Now that the soft limit is integrated to the reclaim directly the whole
soft-limit tree infrastructure is not needed anymore. Rip it out.

Changes v1->v2
- mem_cgroup_reclaimable is no longer used
- test_mem_cgroup_node_reclaimable is not used outside NUMA code

Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
Reviewed-by: Glauber Costa <glommer@xxxxxxxxxx>
Reviewed-by: Tejun Heo <tj@xxxxxxxxxx>
---
mm/memcontrol.c | 265 +-------------------------------------------------------
1 file changed, 2 insertions(+), 263 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ea10f73..cdc8aed 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -39,7 +39,6 @@
#include <linux/limits.h>
#include <linux/export.h>
#include <linux/mutex.h>
-#include <linux/rbtree.h>
#include <linux/slab.h>
#include <linux/swap.h>
#include <linux/swapops.h>
@@ -137,7 +136,6 @@ static const char * const mem_cgroup_lru_names[] = {
*/
enum mem_cgroup_events_target {
MEM_CGROUP_TARGET_THRESH,
- MEM_CGROUP_TARGET_SOFTLIMIT,
MEM_CGROUP_TARGET_NUMAINFO,
MEM_CGROUP_NTARGETS,
};
@@ -173,10 +171,6 @@ struct mem_cgroup_per_zone {

struct mem_cgroup_reclaim_iter reclaim_iter[DEF_PRIORITY + 1];

- 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;
struct mem_cgroup *memcg; /* Back pointer, we cannot */
/* use container_of */
};
@@ -185,26 +179,6 @@ struct mem_cgroup_per_node {
struct mem_cgroup_per_zone zoneinfo[MAX_NR_ZONES];
};

-/*
- * 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;
-
struct mem_cgroup_threshold {
struct eventfd_ctx *eventfd;
u64 threshold;
@@ -523,7 +497,6 @@ static bool move_file(void)
* limit reclaim to prevent infinite loops, if they ever occur.
*/
#define MEM_CGROUP_MAX_RECLAIM_LOOPS 100
-#define MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS 2

enum charge_type {
MEM_CGROUP_CHARGE_TYPE_CACHE = 0,
@@ -754,164 +727,6 @@ page_cgroup_zoneinfo(struct mem_cgroup *memcg, struct page *page)
return mem_cgroup_zoneinfo(memcg, 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 *memcg,
- struct mem_cgroup_per_zone *mz,
- struct mem_cgroup_tree_per_zone *mctz,
- unsigned long long new_usage_in_excess)
-{
- 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 = new_usage_in_excess;
- if (!mz->usage_in_excess)
- return;
- 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;
-}
-
-static void
-__mem_cgroup_remove_exceeded(struct mem_cgroup *memcg,
- struct mem_cgroup_per_zone *mz,
- struct mem_cgroup_tree_per_zone *mctz)
-{
- if (!mz->on_tree)
- return;
- rb_erase(&mz->tree_node, &mctz->rb_root);
- mz->on_tree = false;
-}
-
-static void
-mem_cgroup_remove_exceeded(struct mem_cgroup *memcg,
- struct mem_cgroup_per_zone *mz,
- struct mem_cgroup_tree_per_zone *mctz)
-{
- spin_lock(&mctz->lock);
- __mem_cgroup_remove_exceeded(memcg, mz, mctz);
- spin_unlock(&mctz->lock);
-}
-
-
-static void mem_cgroup_update_tree(struct mem_cgroup *memcg, struct page *page)
-{
- unsigned long long excess;
- struct mem_cgroup_per_zone *mz;
- struct mem_cgroup_tree_per_zone *mctz;
- int nid = page_to_nid(page);
- int zid = page_zonenum(page);
- mctz = soft_limit_tree_from_page(page);
-
- /*
- * Necessary to update all ancestors when hierarchy is used.
- * because their event counter is not touched.
- */
- for (; memcg; memcg = parent_mem_cgroup(memcg)) {
- mz = mem_cgroup_zoneinfo(memcg, nid, zid);
- excess = res_counter_soft_limit_excess(&memcg->res);
- /*
- * We have to update the tree if mz is on RB-tree or
- * mem is over its softlimit.
- */
- if (excess || mz->on_tree) {
- spin_lock(&mctz->lock);
- /* if on-tree, remove it */
- if (mz->on_tree)
- __mem_cgroup_remove_exceeded(memcg, mz, mctz);
- /*
- * Insert again. mz->usage_in_excess will be updated.
- * If excess is 0, no tree ops.
- */
- __mem_cgroup_insert_exceeded(memcg, mz, mctz, excess);
- spin_unlock(&mctz->lock);
- }
- }
-}
-
-static void mem_cgroup_remove_from_trees(struct mem_cgroup *memcg)
-{
- int node, zone;
- struct mem_cgroup_per_zone *mz;
- struct mem_cgroup_tree_per_zone *mctz;
-
- for_each_node(node) {
- for (zone = 0; zone < MAX_NR_ZONES; zone++) {
- mz = mem_cgroup_zoneinfo(memcg, node, zone);
- mctz = soft_limit_tree_node_zone(node, zone);
- mem_cgroup_remove_exceeded(memcg, mz, mctz);
- }
- }
-}
-
-static struct mem_cgroup_per_zone *
-__mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
-{
- struct rb_node *rightmost = NULL;
- struct mem_cgroup_per_zone *mz;
-
-retry:
- mz = NULL;
- rightmost = rb_last(&mctz->rb_root);
- if (!rightmost)
- goto done; /* Nothing to reclaim from */
-
- mz = rb_entry(rightmost, struct mem_cgroup_per_zone, tree_node);
- /*
- * Remove the node now but someone else can add it back,
- * we will to add it back at the end of reclaim to its correct
- * position in the tree.
- */
- __mem_cgroup_remove_exceeded(mz->memcg, mz, mctz);
- if (!res_counter_soft_limit_excess(&mz->memcg->res) ||
- !css_tryget(&mz->memcg->css))
- goto retry;
-done:
- return mz;
-}
-
-static struct mem_cgroup_per_zone *
-mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
-{
- struct mem_cgroup_per_zone *mz;
-
- spin_lock(&mctz->lock);
- mz = __mem_cgroup_largest_soft_limit_node(mctz);
- spin_unlock(&mctz->lock);
- return mz;
-}
-
/*
* Implementation Note: reading percpu statistics for memcg.
*
@@ -1065,9 +880,6 @@ static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
case MEM_CGROUP_TARGET_THRESH:
next = val + THRESHOLDS_EVENTS_TARGET;
break;
- case MEM_CGROUP_TARGET_SOFTLIMIT:
- next = val + SOFTLIMIT_EVENTS_TARGET;
- break;
case MEM_CGROUP_TARGET_NUMAINFO:
next = val + NUMAINFO_EVENTS_TARGET;
break;
@@ -1090,11 +902,8 @@ static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
/* threshold event is triggered in finer grain than soft limit */
if (unlikely(mem_cgroup_event_ratelimit(memcg,
MEM_CGROUP_TARGET_THRESH))) {
- bool do_softlimit;
bool do_numainfo __maybe_unused;

- do_softlimit = mem_cgroup_event_ratelimit(memcg,
- MEM_CGROUP_TARGET_SOFTLIMIT);
#if MAX_NUMNODES > 1
do_numainfo = mem_cgroup_event_ratelimit(memcg,
MEM_CGROUP_TARGET_NUMAINFO);
@@ -1102,8 +911,6 @@ static void memcg_check_events(struct mem_cgroup *memcg, struct page *page)
preempt_enable();

mem_cgroup_threshold(memcg);
- if (unlikely(do_softlimit))
- mem_cgroup_update_tree(memcg, page);
#if MAX_NUMNODES > 1
if (unlikely(do_numainfo))
atomic_inc(&memcg->numainfo_events);
@@ -1964,6 +1771,7 @@ static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
return total;
}

+#if MAX_NUMNODES > 1
/**
* test_mem_cgroup_node_reclaimable
* @memcg: the target memcg
@@ -1986,7 +1794,6 @@ static bool test_mem_cgroup_node_reclaimable(struct mem_cgroup *memcg,
return false;

}
-#if MAX_NUMNODES > 1

/*
* Always updating the nodemask is not very good - even if we have an empty
@@ -2054,51 +1861,12 @@ int mem_cgroup_select_victim_node(struct mem_cgroup *memcg)
return node;
}

-/*
- * Check all nodes whether it contains reclaimable pages or not.
- * For quick scan, we make use of scan_nodes. This will allow us to skip
- * unused nodes. But scan_nodes is lazily updated and may not cotain
- * enough new information. We need to do double check.
- */
-static bool mem_cgroup_reclaimable(struct mem_cgroup *memcg, bool noswap)
-{
- int nid;
-
- /*
- * quick check...making use of scan_node.
- * We can skip unused nodes.
- */
- if (!nodes_empty(memcg->scan_nodes)) {
- for (nid = first_node(memcg->scan_nodes);
- nid < MAX_NUMNODES;
- nid = next_node(nid, memcg->scan_nodes)) {
-
- if (test_mem_cgroup_node_reclaimable(memcg, nid, noswap))
- return true;
- }
- }
- /*
- * Check rest of nodes.
- */
- for_each_node_state(nid, N_MEMORY) {
- if (node_isset(nid, memcg->scan_nodes))
- continue;
- if (test_mem_cgroup_node_reclaimable(memcg, nid, noswap))
- return true;
- }
- return false;
-}
-
#else
int mem_cgroup_select_victim_node(struct mem_cgroup *memcg)
{
return 0;
}

-static bool mem_cgroup_reclaimable(struct mem_cgroup *memcg, bool noswap)
-{
- return test_mem_cgroup_node_reclaimable(memcg, 0, noswap);
-}
#endif

/*
@@ -2973,9 +2741,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
unlock_page_cgroup(pc);

/*
- * "charge_statistics" updated event counter. Then, check it.
- * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree.
- * if they exceeds softlimit.
+ * "charge_statistics" updated event counter.
*/
memcg_check_events(memcg, page);
}
@@ -6112,8 +5878,6 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
for (zone = 0; zone < MAX_NR_ZONES; zone++) {
mz = &pn->zoneinfo[zone];
lruvec_init(&mz->lruvec);
- mz->usage_in_excess = 0;
- mz->on_tree = false;
mz->memcg = memcg;
}
memcg->nodeinfo[node] = pn;
@@ -6169,7 +5933,6 @@ static void __mem_cgroup_free(struct mem_cgroup *memcg)
int node;
size_t size = memcg_size();

- mem_cgroup_remove_from_trees(memcg);
free_css_id(&mem_cgroup_subsys, &memcg->css);

for_each_node(node)
@@ -6251,29 +6014,6 @@ struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
}
EXPORT_SYMBOL(parent_mem_cgroup);

-static void __init 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(node) {
- tmp = node;
- if (!node_state(node, N_NORMAL_MEMORY))
- tmp = -1;
- rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL, tmp);
- BUG_ON(!rtpn);
-
- 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);
- }
- }
-}
-
static struct cgroup_subsys_state * __ref
mem_cgroup_css_alloc(struct cgroup *cont)
{
@@ -7066,7 +6806,6 @@ static int __init mem_cgroup_init(void)
{
hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
enable_swap_cgroup();
- mem_cgroup_soft_limit_tree_init();
memcg_stock_init();
return 0;
}
--
1.8.3.1

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