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memcg: use CSS ID
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Assigning CSS ID for each memcg and use css_get_next() for scanning hierarchy.

	Assume folloing tree.

	group_A (ID=3)
		/01 (ID=4)
		   /0A (ID=7)
		/02 (ID=10)
	group_B (ID=5)
	and task in group_A/01/0A hits limit at group_A.

	reclaim will be done in following order (round-robin).
	group_A(3) -> group_A/01 (4) -> group_A/01/0A (7) -> group_A/02(10)
	-> group_A -> .....

	Round robin by ID. The last visited cgroup is recorded and restart
	from it when it start reclaim again.
	(More smart algorithm can be implemented..)

	No cgroup_mutex or hierarchy_mutex is required.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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KAMEZAWA Hiroyuki authored and Linus Torvalds committed Apr 3, 2009
1 parent b4046f0 commit 04046e1
Showing 1 changed file with 82 additions and 138 deletions.
220 changes: 82 additions & 138 deletions mm/memcontrol.c
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Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,15 @@ static s64 mem_cgroup_read_stat(struct mem_cgroup_stat *stat,
return ret;
}

static s64 mem_cgroup_local_usage(struct mem_cgroup_stat *stat)
{
s64 ret;

ret = mem_cgroup_read_stat(stat, MEM_CGROUP_STAT_CACHE);
ret += mem_cgroup_read_stat(stat, MEM_CGROUP_STAT_RSS);
return ret;
}

/*
* per-zone information in memory controller.
*/
Expand Down Expand Up @@ -154,9 +163,9 @@ struct mem_cgroup {

/*
* While reclaiming in a hiearchy, we cache the last child we
* reclaimed from. Protected by hierarchy_mutex
* reclaimed from.
*/
struct mem_cgroup *last_scanned_child;
int last_scanned_child;
/*
* Should the accounting and control be hierarchical, per subtree?
*/
Expand Down Expand Up @@ -629,103 +638,6 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
#define mem_cgroup_from_res_counter(counter, member) \
container_of(counter, struct mem_cgroup, member)

/*
* This routine finds the DFS walk successor. This routine should be
* called with hierarchy_mutex held
*/
static struct mem_cgroup *
__mem_cgroup_get_next_node(struct mem_cgroup *curr, struct mem_cgroup *root_mem)
{
struct cgroup *cgroup, *curr_cgroup, *root_cgroup;

curr_cgroup = curr->css.cgroup;
root_cgroup = root_mem->css.cgroup;

if (!list_empty(&curr_cgroup->children)) {
/*
* Walk down to children
*/
cgroup = list_entry(curr_cgroup->children.next,
struct cgroup, sibling);
curr = mem_cgroup_from_cont(cgroup);
goto done;
}

visit_parent:
if (curr_cgroup == root_cgroup) {
/* caller handles NULL case */
curr = NULL;
goto done;
}

/*
* Goto next sibling
*/
if (curr_cgroup->sibling.next != &curr_cgroup->parent->children) {
cgroup = list_entry(curr_cgroup->sibling.next, struct cgroup,
sibling);
curr = mem_cgroup_from_cont(cgroup);
goto done;
}

/*
* Go up to next parent and next parent's sibling if need be
*/
curr_cgroup = curr_cgroup->parent;
goto visit_parent;

done:
return curr;
}

/*
* Visit the first child (need not be the first child as per the ordering
* of the cgroup list, since we track last_scanned_child) of @mem and use
* that to reclaim free pages from.
*/
static struct mem_cgroup *
mem_cgroup_get_next_node(struct mem_cgroup *root_mem)
{
struct cgroup *cgroup;
struct mem_cgroup *orig, *next;
bool obsolete;

/*
* Scan all children under the mem_cgroup mem
*/
mutex_lock(&mem_cgroup_subsys.hierarchy_mutex);

orig = root_mem->last_scanned_child;
obsolete = mem_cgroup_is_obsolete(orig);

if (list_empty(&root_mem->css.cgroup->children)) {
/*
* root_mem might have children before and last_scanned_child
* may point to one of them. We put it later.
*/
if (orig)
VM_BUG_ON(!obsolete);
next = NULL;
goto done;
}

if (!orig || obsolete) {
cgroup = list_first_entry(&root_mem->css.cgroup->children,
struct cgroup, sibling);
next = mem_cgroup_from_cont(cgroup);
} else
next = __mem_cgroup_get_next_node(orig, root_mem);

done:
if (next)
mem_cgroup_get(next);
root_mem->last_scanned_child = next;
if (orig)
mem_cgroup_put(orig);
mutex_unlock(&mem_cgroup_subsys.hierarchy_mutex);
return (next) ? next : root_mem;
}

static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem)
{
if (do_swap_account) {
Expand Down Expand Up @@ -755,46 +667,79 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
}

/*
* Dance down the hierarchy if needed to reclaim memory. We remember the
* last child we reclaimed from, so that we don't end up penalizing
* one child extensively based on its position in the children list.
* Visit the first child (need not be the first child as per the ordering
* of the cgroup list, since we track last_scanned_child) of @mem and use
* that to reclaim free pages from.
*/
static struct mem_cgroup *
mem_cgroup_select_victim(struct mem_cgroup *root_mem)
{
struct mem_cgroup *ret = NULL;
struct cgroup_subsys_state *css;
int nextid, found;

if (!root_mem->use_hierarchy) {
css_get(&root_mem->css);
ret = root_mem;
}

while (!ret) {
rcu_read_lock();
nextid = root_mem->last_scanned_child + 1;
css = css_get_next(&mem_cgroup_subsys, nextid, &root_mem->css,
&found);
if (css && css_tryget(css))
ret = container_of(css, struct mem_cgroup, css);

rcu_read_unlock();
/* Updates scanning parameter */
spin_lock(&root_mem->reclaim_param_lock);
if (!css) {
/* this means start scan from ID:1 */
root_mem->last_scanned_child = 0;
} else
root_mem->last_scanned_child = found;
spin_unlock(&root_mem->reclaim_param_lock);
}

return ret;
}

/*
* Scan the hierarchy if needed to reclaim memory. We remember the last child
* we reclaimed from, so that we don't end up penalizing one child extensively
* based on its position in the children list.
*
* root_mem is the original ancestor that we've been reclaim from.
*
* We give up and return to the caller when we visit root_mem twice.
* (other groups can be removed while we're walking....)
*/
static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
gfp_t gfp_mask, bool noswap)
{
struct mem_cgroup *next_mem;
int ret = 0;

/*
* Reclaim unconditionally and don't check for return value.
* We need to reclaim in the current group and down the tree.
* One might think about checking for children before reclaiming,
* but there might be left over accounting, even after children
* have left.
*/
ret += try_to_free_mem_cgroup_pages(root_mem, gfp_mask, noswap,
get_swappiness(root_mem));
if (mem_cgroup_check_under_limit(root_mem))
return 1; /* indicate reclaim has succeeded */
if (!root_mem->use_hierarchy)
return ret;

next_mem = mem_cgroup_get_next_node(root_mem);

while (next_mem != root_mem) {
if (mem_cgroup_is_obsolete(next_mem)) {
next_mem = mem_cgroup_get_next_node(root_mem);
struct mem_cgroup *victim;
int ret, total = 0;
int loop = 0;

while (loop < 2) {
victim = mem_cgroup_select_victim(root_mem);
if (victim == root_mem)
loop++;
if (!mem_cgroup_local_usage(&victim->stat)) {
/* this cgroup's local usage == 0 */
css_put(&victim->css);
continue;
}
ret += try_to_free_mem_cgroup_pages(next_mem, gfp_mask, noswap,
get_swappiness(next_mem));
/* we use swappiness of local cgroup */
ret = try_to_free_mem_cgroup_pages(victim, gfp_mask, noswap,
get_swappiness(victim));
css_put(&victim->css);
total += ret;
if (mem_cgroup_check_under_limit(root_mem))
return 1; /* indicate reclaim has succeeded */
next_mem = mem_cgroup_get_next_node(root_mem);
return 1 + total;
}
return ret;
return total;
}

bool mem_cgroup_oom_called(struct task_struct *task)
Expand Down Expand Up @@ -1324,8 +1269,8 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
res_counter_uncharge(&mem->res, PAGE_SIZE);
if (do_swap_account && (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT))
res_counter_uncharge(&mem->memsw, PAGE_SIZE);

mem_cgroup_charge_statistics(mem, pc, false);

ClearPageCgroupUsed(pc);
/*
* pc->mem_cgroup is not cleared here. It will be accessed when it's
Expand Down Expand Up @@ -2178,6 +2123,8 @@ static void __mem_cgroup_free(struct mem_cgroup *mem)
{
int node;

free_css_id(&mem_cgroup_subsys, &mem->css);

for_each_node_state(node, N_POSSIBLE)
free_mem_cgroup_per_zone_info(mem, node);

Expand Down Expand Up @@ -2228,11 +2175,12 @@ static struct cgroup_subsys_state * __ref
mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
{
struct mem_cgroup *mem, *parent;
long error = -ENOMEM;
int node;

mem = mem_cgroup_alloc();
if (!mem)
return ERR_PTR(-ENOMEM);
return ERR_PTR(error);

for_each_node_state(node, N_POSSIBLE)
if (alloc_mem_cgroup_per_zone_info(mem, node))
Expand Down Expand Up @@ -2260,7 +2208,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
res_counter_init(&mem->res, NULL);
res_counter_init(&mem->memsw, NULL);
}
mem->last_scanned_child = NULL;
mem->last_scanned_child = 0;
spin_lock_init(&mem->reclaim_param_lock);

if (parent)
Expand All @@ -2269,7 +2217,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
return &mem->css;
free_out:
__mem_cgroup_free(mem);
return ERR_PTR(-ENOMEM);
return ERR_PTR(error);
}

static int mem_cgroup_pre_destroy(struct cgroup_subsys *ss,
Expand All @@ -2284,12 +2232,7 @@ static void mem_cgroup_destroy(struct cgroup_subsys *ss,
struct cgroup *cont)
{
struct mem_cgroup *mem = mem_cgroup_from_cont(cont);
struct mem_cgroup *last_scanned_child = mem->last_scanned_child;

if (last_scanned_child) {
VM_BUG_ON(!mem_cgroup_is_obsolete(last_scanned_child));
mem_cgroup_put(last_scanned_child);
}
mem_cgroup_put(mem);
}

Expand Down Expand Up @@ -2328,6 +2271,7 @@ struct cgroup_subsys mem_cgroup_subsys = {
.populate = mem_cgroup_populate,
.attach = mem_cgroup_move_task,
.early_init = 0,
.use_id = 1,
};

#ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
Expand Down

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