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memcg: use for_each_mem_cgroup 

In memory cgroup management, we sometimes have to walk through
subhierarchy of cgroup to gather informaiton, or lock something, etc.

Now, to do that, mem_cgroup_walk_tree() function is provided.  It calls
given callback function per cgroup found.  But the bad thing is that it
has to pass a fixed style function and argument, "void*" and it adds much
type casting to memcontrol.c.

To make the code clean, this patch replaces walk_tree() with

  for_each_mem_cgroup_tree(iter, root)

An iterator style call.  The good point is that iterator call doesn't have
to assume what kind of function is called under it.  A bad point is that
it may cause reference-count leak if a caller use "break" from the loop by
mistake.

I think the benefit is larger.  The modified code seems straigtforward and
easy to read because we don't have misterious callbacks and pointer cast.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
KAMEZAWA Hiroyuki 2010-10-27 15:33:41 -07:00 committed by Linus Torvalds
parent 32047e2a85
commit 7d74b06f24
1 changed files with 92 additions and 96 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

188
mm/memcontrol.c
View File

@ -660,41 +660,58 @@ static struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
return mem;
}
/*
* Call callback function against all cgroup under hierarchy tree.
*/
static int mem_cgroup_walk_tree(struct mem_cgroup *root, void *data,
int (*func)(struct mem_cgroup *, void *))
/* The caller has to guarantee "mem" exists before calling this */
static struct mem_cgroup *mem_cgroup_start_loop(struct mem_cgroup *mem)
{
int found, ret, nextid;
struct cgroup_subsys_state *css;
struct mem_cgroup *mem;
if (!root->use_hierarchy)
return (*func)(root, data);
nextid = 1;
do {
ret = 0;
mem = NULL;
rcu_read_lock();
css = css_get_next(&mem_cgroup_subsys, nextid, &root->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;
if (mem && css_tryget(&mem->css))
return mem;
return NULL;
}
static struct mem_cgroup *mem_cgroup_get_next(struct mem_cgroup *iter,
struct mem_cgroup *root,
bool cond)
{
int nextid = css_id(&iter->css) + 1;
int found;
int hierarchy_used;
struct cgroup_subsys_state *css;
hierarchy_used = iter->use_hierarchy;
css_put(&iter->css);
if (!cond || !hierarchy_used)
return NULL;
do {
iter = NULL;
rcu_read_lock();
css = css_get_next(&mem_cgroup_subsys, nextid,
&root->css, &found);
if (css && css_tryget(css))
iter = container_of(css, struct mem_cgroup, css);
rcu_read_unlock();
/* If css is NULL, no more cgroups will be found */
nextid = found + 1;
} while (css && !iter);
return iter;
}
/*
* for_eacn_mem_cgroup_tree() for visiting all cgroup under tree. Please
* be careful that "break" loop is not allowed. We have reference count.
* Instead of that modify "cond" to be false and "continue" to exit the loop.
*/
#define for_each_mem_cgroup_tree_cond(iter, root, cond) \
for (iter = mem_cgroup_start_loop(root);\
iter != NULL;\
iter = mem_cgroup_get_next(iter, root, cond))
#define for_each_mem_cgroup_tree(iter, root) \
for_each_mem_cgroup_tree_cond(iter, root, true)
static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
{
return (mem == root_mem_cgroup);
@ -1132,13 +1149,6 @@ static bool mem_cgroup_wait_acct_move(struct mem_cgroup *mem)
return false;
}
static int mem_cgroup_count_children_cb(struct mem_cgroup *mem, void *data)
{
int *val = data;
(*val)++;
return 0;
}
/**
* mem_cgroup_print_oom_info: Called from OOM with tasklist_lock held in read mode.
* @memcg: The memory cgroup that went over limit
@ -1213,7 +1223,10 @@ done:
static int mem_cgroup_count_children(struct mem_cgroup *mem)
{
int num = 0;
mem_cgroup_walk_tree(mem, &num, mem_cgroup_count_children_cb);
struct mem_cgroup *iter;
for_each_mem_cgroup_tree(iter, mem)
num++;
return num;
}
@ -1362,49 +1375,39 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
return total;
}
static int mem_cgroup_oom_lock_cb(struct mem_cgroup *mem, void *data)
{
int *val = (int *)data;
int x;
/*
* Logically, we can stop scanning immediately when we find
* a memcg is already locked. But condidering unlock ops and
* creation/removal of memcg, scan-all is simple operation.
*/
x = atomic_inc_return(&mem->oom_lock);
*val = max(x, *val);
return 0;
}
/*
* Check OOM-Killer is already running under our hierarchy.
* If someone is running, return false.
*/
static bool mem_cgroup_oom_lock(struct mem_cgroup *mem)
{
int lock_count = 0;
int x, lock_count = 0;
struct mem_cgroup *iter;
mem_cgroup_walk_tree(mem, &lock_count, mem_cgroup_oom_lock_cb);
for_each_mem_cgroup_tree(iter, mem) {
x = atomic_inc_return(&iter->oom_lock);
lock_count = max(x, lock_count);
}
if (lock_count == 1)
return true;
return false;
}
static int mem_cgroup_oom_unlock_cb(struct mem_cgroup *mem, void *data)
static int mem_cgroup_oom_unlock(struct mem_cgroup *mem)
{
struct mem_cgroup *iter;
/*
* When a new child is created while the hierarchy is under oom,
* mem_cgroup_oom_lock() may not be called. We have to use
* atomic_add_unless() here.
*/
atomic_add_unless(&mem->oom_lock, -1, 0);
for_each_mem_cgroup_tree(iter, mem)
atomic_add_unless(&iter->oom_lock, -1, 0);
return 0;
}
static void mem_cgroup_oom_unlock(struct mem_cgroup *mem)
{
mem_cgroup_walk_tree(mem, NULL, mem_cgroup_oom_unlock_cb);
}
static DEFINE_MUTEX(memcg_oom_mutex);
static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);
@ -3207,33 +3210,25 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
return retval;
}
struct mem_cgroup_idx_data {
s64 val;
enum mem_cgroup_stat_index idx;
};
static int
mem_cgroup_get_idx_stat(struct mem_cgroup *mem, void *data)
static u64 mem_cgroup_get_recursive_idx_stat(struct mem_cgroup *mem,
enum mem_cgroup_stat_index idx)
{
struct mem_cgroup_idx_data *d = data;
d->val += mem_cgroup_read_stat(mem, d->idx);
return 0;
}
struct mem_cgroup *iter;
s64 val = 0;
static void
mem_cgroup_get_recursive_idx_stat(struct mem_cgroup *mem,
enum mem_cgroup_stat_index idx, s64 *val)
{
struct mem_cgroup_idx_data d;
d.idx = idx;
d.val = 0;
mem_cgroup_walk_tree(mem, &d, mem_cgroup_get_idx_stat);
*val = d.val;
/* each per cpu's value can be minus.Then, use s64 */
for_each_mem_cgroup_tree(iter, mem)
val += mem_cgroup_read_stat(iter, idx);
if (val < 0) /* race ? */
val = 0;
return val;
}
static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
{
u64 idx_val, val;
u64 val;
if (!mem_cgroup_is_root(mem)) {
if (!swap)
@ -3242,16 +3237,12 @@ static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
return res_counter_read_u64(&mem->memsw, RES_USAGE);
}
mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_CACHE, &idx_val);
val = idx_val;
mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_RSS, &idx_val);
val += idx_val;
val = mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_CACHE);
val += mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_RSS);
if (swap) {
mem_cgroup_get_recursive_idx_stat(mem,
MEM_CGROUP_STAT_SWAPOUT, &idx_val);
val += idx_val;
}
if (swap)
val += mem_cgroup_get_recursive_idx_stat(mem,
MEM_CGROUP_STAT_SWAPOUT);
return val << PAGE_SHIFT;
}
@ -3459,9 +3450,9 @@ struct {
};
static int mem_cgroup_get_local_stat(struct mem_cgroup *mem, void *data)
static void
mem_cgroup_get_local_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
{
struct mcs_total_stat *s = data;
s64 val;
/* per cpu stat */
@ -3491,13 +3482,15 @@ static int mem_cgroup_get_local_stat(struct mem_cgroup *mem, void *data)
s->stat[MCS_ACTIVE_FILE] += val * PAGE_SIZE;
val = mem_cgroup_get_local_zonestat(mem, LRU_UNEVICTABLE);
s->stat[MCS_UNEVICTABLE] += val * PAGE_SIZE;
return 0;
}
static void
mem_cgroup_get_total_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
{
mem_cgroup_walk_tree(mem, s, mem_cgroup_get_local_stat);
struct mem_cgroup *iter;
for_each_mem_cgroup_tree(iter, mem)
mem_cgroup_get_local_stat(iter, s);
}
static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
@ -3674,7 +3667,7 @@ static int compare_thresholds(const void *a, const void *b)
return _a->threshold - _b->threshold;
}
static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem, void *data)
static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem)
{
struct mem_cgroup_eventfd_list *ev;
@ -3685,7 +3678,10 @@ static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem, void *data)
static void mem_cgroup_oom_notify(struct mem_cgroup *mem)
{
mem_cgroup_walk_tree(mem, NULL, mem_cgroup_oom_notify_cb);
struct mem_cgroup *iter;
for_each_mem_cgroup_tree(iter, mem)
mem_cgroup_oom_notify_cb(iter);
}
static int mem_cgroup_usage_register_event(struct cgroup *cgrp,