[PATCH][-mm] memcg : memory cgroup cpu hotplug support update.

KAMEZAWA Hiroyuki
2010-09-16T05:51:33Z

This is onto The mm-of-the-moment snapshot 2010-09-15-16-21.

==
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

Now, memory cgroup uses for_each_possible_cpu() for percpu stat handling.
It's just because cpu hotplug handler doesn't handle them.
On the other hand, per-cpu usage counter cache is maintained per cpu and
it's cpu hotplug aware.

This patch adds a cpu hotplug hanlder and replaces for_each_possible_cpu()
with for_each_online_cpu(). And this merges new callbacks with old
callbacks.(IOW, memcg has only one cpu-hotplug handler.)

For this purpose, mem_cgroup_walk_all() is added.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
---
mm/memcontrol.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 98 insertions(+), 20 deletions(-)

Index: mmotm-0915/mm/memcontrol.c
===================================================================
--- mmotm-0915.orig/mm/memcontrol.c
+++ mmotm-0915/mm/memcontrol.c
@@ -89,7 +89,10 @@ enum mem_cgroup_stat_index {
MEM_CGROUP_STAT_PGPGIN_COUNT, /* # of pages paged in */
MEM_CGROUP_STAT_PGPGOUT_COUNT, /* # of pages paged out */
MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
- MEM_CGROUP_EVENTS, /* incremented at every pagein/pageout */
+ MEM_CGROUP_STAT_DATA, /* stat above this is for statistics */
+
+ MEM_CGROUP_EVENTS = MEM_CGROUP_STAT_DATA,
+ /* incremented at every pagein/pageout */
MEM_CGROUP_ON_MOVE, /* someone is moving account between groups */

MEM_CGROUP_STAT_NSTATS,
@@ -537,7 +540,7 @@ static s64 mem_cgroup_read_stat(struct m
int cpu;
s64 val = 0;

- for_each_possible_cpu(cpu)
+ for_each_online_cpu(cpu)
val += per_cpu(mem->stat->count[idx], cpu);
return val;
}
@@ -700,6 +703,35 @@ static inline bool mem_cgroup_is_root(st
return (mem == root_mem_cgroup);
}

+static int mem_cgroup_walk_all(void *data,
+ int (*func)(struct mem_cgroup *, void *))
+{
+ int found, ret, nextid;
+ struct cgroup_subsys_state *css;
+ struct mem_cgroup *mem;
+
+ nextid = 1;
+ do {
+ ret = 0;
+ mem = NULL;
+
+ rcu_read_lock();
+ css = css_get_next(&mem_cgroup_subsys, nextid,
+ &root_mem_cgroup->css, &found);
+ if (css && css_tryget(css))
+ mem = container_of(css, struct mem_cgroup, css);
+ rcu_read_unlock();
+
+ if (mem) {
+ ret = (*func)(mem, data);
+ css_put(&mem->css);
+ }
+ nextid = found + 1;
+ } while (!ret && css);
+
+ return ret;
+}
+
/*
* Following LRU functions are allowed to be used without PCG_LOCK.
* Operations are called by routine of global LRU independently from memcg.
@@ -1056,11 +1088,12 @@ static void mem_cgroup_start_move(struct
{
int cpu;
/* Because this is for moving account, reuse mc.lock */
+ get_online_cpus();
spin_lock(&mc.lock);
- for_each_possible_cpu(cpu)
+ for_each_online_cpu(cpu)
per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) += 1;
spin_unlock(&mc.lock);
-
+ put_online_cpus();
synchronize_rcu();
}

@@ -1070,10 +1103,12 @@ static void mem_cgroup_end_move(struct m

if (!mem)
return;
+ get_online_cpus();
spin_lock(&mc.lock);
- for_each_possible_cpu(cpu)
+ for_each_online_cpu(cpu)
per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) -= 1;
spin_unlock(&mc.lock);
+ put_online_cpus();
}
/*
* 2 routines for checking "mem" is under move_account() or not.
@@ -1673,20 +1708,6 @@ static void drain_all_stock_sync(void)
atomic_dec(&memcg_drain_count);
}

-static int __cpuinit memcg_stock_cpu_callback(struct notifier_block *nb,
- unsigned long action,
- void *hcpu)
-{
- int cpu = (unsigned long)hcpu;
- struct memcg_stock_pcp *stock;
-
- if (action != CPU_DEAD)
- return NOTIFY_OK;
- stock = &per_cpu(memcg_stock, cpu);
- drain_stock(stock);
- return NOTIFY_OK;
-}
-

/* See __mem_cgroup_try_charge() for details */
enum {
@@ -3465,6 +3486,7 @@ static int mem_cgroup_get_local_stat(str
s64 val;

/* per cpu stat */
+ get_online_cpus();
val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
s->stat[MCS_CACHE] += val * PAGE_SIZE;
val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
@@ -3479,6 +3501,7 @@ static int mem_cgroup_get_local_stat(str
val = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_SWAPOUT);
s->stat[MCS_SWAP] += val * PAGE_SIZE;
}
+ put_online_cpus();

/* per zone stat */
val = mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON);
@@ -3508,7 +3531,9 @@ static int mem_control_stat_show(struct
int i;

memset(&mystat, 0, sizeof(mystat));
+ get_online_cpus();
mem_cgroup_get_local_stat(mem_cont, &mystat);
+ put_online_cpus();

for (i = 0; i < NR_MCS_STAT; i++) {
if (i == MCS_SWAP && !do_swap_account)
@@ -3526,7 +3551,9 @@ static int mem_control_stat_show(struct
}

memset(&mystat, 0, sizeof(mystat));
+ get_online_cpus();
mem_cgroup_get_total_stat(mem_cont, &mystat);
+ put_online_cpus();
for (i = 0; i < NR_MCS_STAT; i++) {
if (i == MCS_SWAP && !do_swap_account)
continue;
@@ -4036,6 +4063,57 @@ static int register_memsw_files(struct c
}
#endif

+/*
+ * CPU Hotplug handling.
+ */
+static int synchronize_move_stat(struct mem_cgroup *mem, void *data)
+{
+ long cpu = (long)data;
+ s64 x = this_cpu_read(mem->stat->count[MEM_CGROUP_ON_MOVE]);
+ /* All cpus should have the same value */
+ per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) = x;
+ return 0;
+}
+
+static int drain_all_percpu(struct mem_cgroup *mem, void *data)
+{
+ long cpu = (long)(data);
+ int i;
+ /* Drain data from dying cpu and move to local cpu */
+ for (i = 0; i < MEM_CGROUP_STAT_DATA; i++) {
+ s64 data = per_cpu(mem->stat->count[i], cpu);
+ per_cpu(mem->stat->count[i], cpu) = 0;
+ this_cpu_add(mem->stat->count[i], data);
+ }
+ /* Reset Move Count */
+ per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) = 0;
+ return 0;
+}
+
+static int __cpuinit memcg_cpuhotplug_callback(struct notifier_block *nb,
+ unsigned long action,
+ void *hcpu)
+{
+ long cpu = (unsigned long)hcpu;
+ struct memcg_stock_pcp *stock;
+
+ if (action == CPU_ONLINE) {
+ mem_cgroup_walk_all((void *)cpu, synchronize_move_stat);
+ return NOTIFY_OK;
+ }
+ if ((action != CPU_DEAD) || (action != CPU_DEAD_FROZEN))
+ return NOTIFY_OK;
+
+ /* Drain counters...for all memcgs. */
+ mem_cgroup_walk_all((void *)cpu, drain_all_percpu);
+
+ /* Drain Cached resources */
+ stock = &per_cpu(memcg_stock, cpu);
+ drain_stock(stock);
+
+ return NOTIFY_OK;
+}
+
static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *mem, int node)
{
struct mem_cgroup_per_node *pn;
@@ -4224,7 +4302,7 @@ mem_cgroup_create(struct cgroup_subsys *
&per_cpu(memcg_stock, cpu);
INIT_WORK(&stock->work, drain_local_stock);
}
- hotcpu_notifier(memcg_stock_cpu_callback, 0);
+ hotcpu_notifier(memcg_cpuhotplug_callback, 0);
} else {
parent = mem_cgroup_from_cont(cont->parent);
mem->use_hierarchy = parent->use_hierarchy;