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memcg: improve performance in moving swap charge

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Try to reduce overheads in moving swap charge by:

- Adds a new function(__mem_cgroup_put), which takes "count" as a arg and
  decrement mem->refcnt by "count".
- Removed res_counter_uncharge, css_put, and mem_cgroup_put from the path
  of moving swap account, and consolidate all of them into mem_cgroup_clear_mc.
  We cannot do that about mc.to->refcnt.

These changes reduces the overhead from 1.35sec to 0.9sec to move charges
of 1G anonymous memory(including 500MB swap) in my test environment.

Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.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:
Daisuke Nishimura 2010-03-10 15:22:18 -08:00 committed by Linus Torvalds
parent 024914477e
commit 483c30b514
1 changed files with 61 additions and 16 deletions
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77
mm/memcontrol.c
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@ -255,6 +255,7 @@ static struct move_charge_struct {
struct mem_cgroup *to;
unsigned long precharge;
unsigned long moved_charge;
unsigned long moved_swap;
struct task_struct *moving_task; /* a task moving charges */
wait_queue_head_t waitq; /* a waitq for other context */
} mc = {
@ -2277,6 +2278,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent)
* @entry: swap entry to be moved
* @from: mem_cgroup which the entry is moved from
* @to: mem_cgroup which the entry is moved to
* @need_fixup: whether we should fixup res_counters and refcounts.
*
* It succeeds only when the swap_cgroup's record for this entry is the same
* as the mem_cgroup's id of @from.
@ -2287,7 +2289,7 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent)
* both res and memsw, and called css_get().
*/
static int mem_cgroup_move_swap_account(swp_entry_t entry,
struct mem_cgroup *from, struct mem_cgroup *to)
struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup)
{
unsigned short old_id, new_id;
@ -2295,27 +2297,36 @@ static int mem_cgroup_move_swap_account(swp_entry_t entry,
new_id = css_id(&to->css);
if (swap_cgroup_cmpxchg(entry, old_id, new_id) == old_id) {
if (!mem_cgroup_is_root(from))
res_counter_uncharge(&from->memsw, PAGE_SIZE);
mem_cgroup_swap_statistics(from, false);
mem_cgroup_put(from);
/*
* we charged both to->res and to->memsw, so we should uncharge
* to->res.
*/
if (!mem_cgroup_is_root(to))
res_counter_uncharge(&to->res, PAGE_SIZE);
mem_cgroup_swap_statistics(to, true);
/*
* This function is only called from task migration context now.
* It postpones res_counter and refcount handling till the end
* of task migration(mem_cgroup_clear_mc()) for performance
* improvement. But we cannot postpone mem_cgroup_get(to)
* because if the process that has been moved to @to does
* swap-in, the refcount of @to might be decreased to 0.
*/
mem_cgroup_get(to);
css_put(&to->css);
if (need_fixup) {
if (!mem_cgroup_is_root(from))
res_counter_uncharge(&from->memsw, PAGE_SIZE);
mem_cgroup_put(from);
/*
* we charged both to->res and to->memsw, so we should
* uncharge to->res.
*/
if (!mem_cgroup_is_root(to))
res_counter_uncharge(&to->res, PAGE_SIZE);
css_put(&to->css);
}
return 0;
}
return -EINVAL;
}
#else
static inline int mem_cgroup_move_swap_account(swp_entry_t entry,
struct mem_cgroup *from, struct mem_cgroup *to)
struct mem_cgroup *from, struct mem_cgroup *to, bool need_fixup)
{
return -EINVAL;
}
@ -3398,9 +3409,9 @@ static void mem_cgroup_get(struct mem_cgroup *mem)
atomic_inc(&mem->refcnt);
}
static void mem_cgroup_put(struct mem_cgroup *mem)
static void __mem_cgroup_put(struct mem_cgroup *mem, int count)
{
if (atomic_dec_and_test(&mem->refcnt)) {
if (atomic_sub_and_test(count, &mem->refcnt)) {
struct mem_cgroup *parent = parent_mem_cgroup(mem);
__mem_cgroup_free(mem);
if (parent)
@ -3408,6 +3419,11 @@ static void mem_cgroup_put(struct mem_cgroup *mem)
}
}
static void mem_cgroup_put(struct mem_cgroup *mem)
{
__mem_cgroup_put(mem, 1);
}
/*
* Returns the parent mem_cgroup in memcgroup hierarchy with hierarchy enabled.
*/
@ -3789,6 +3805,29 @@ static void mem_cgroup_clear_mc(void)
__mem_cgroup_cancel_charge(mc.from, mc.moved_charge);
mc.moved_charge = 0;
}
/* we must fixup refcnts and charges */
if (mc.moved_swap) {
WARN_ON_ONCE(mc.moved_swap > INT_MAX);
/* uncharge swap account from the old cgroup */
if (!mem_cgroup_is_root(mc.from))
res_counter_uncharge(&mc.from->memsw,
PAGE_SIZE * mc.moved_swap);
__mem_cgroup_put(mc.from, mc.moved_swap);
if (!mem_cgroup_is_root(mc.to)) {
/*
* we charged both to->res and to->memsw, so we should
* uncharge to->res.
*/
res_counter_uncharge(&mc.to->res,
PAGE_SIZE * mc.moved_swap);
VM_BUG_ON(test_bit(CSS_ROOT, &mc.to->css.flags));
__css_put(&mc.to->css, mc.moved_swap);
}
/* we've already done mem_cgroup_get(mc.to) */
mc.moved_swap = 0;
}
mc.from = NULL;
mc.to = NULL;
mc.moving_task = NULL;
@ -3818,11 +3857,13 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
VM_BUG_ON(mc.to);
VM_BUG_ON(mc.precharge);
VM_BUG_ON(mc.moved_charge);
VM_BUG_ON(mc.moved_swap);
VM_BUG_ON(mc.moving_task);
mc.from = from;
mc.to = mem;
mc.precharge = 0;
mc.moved_charge = 0;
mc.moved_swap = 0;
mc.moving_task = current;
ret = mem_cgroup_precharge_mc(mm);
@ -3883,8 +3924,12 @@ put: /* is_target_pte_for_mc() gets the page */
break;
case MC_TARGET_SWAP:
ent = target.ent;
if (!mem_cgroup_move_swap_account(ent, mc.from, mc.to))
if (!mem_cgroup_move_swap_account(ent,
mc.from, mc.to, false)) {
mc.precharge--;
/* we fixup refcnts and charges later. */
mc.moved_swap++;
}
break;
default:
break;