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SubjectRe: [RFC][PATCH -mm 0/7] memcg: lockless page_cgroup v1
On Wed, 20 Aug 2008 20:00:06 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> > Known problem: force_emtpy is broken...so rmdir will struck into nightmare.
> > It's because of patch 2/7.
> > will be fixed in the next version.
> >
>
This is a new routine for force_empty. Assumes init_mem_cgroup has no limit.
(lockless page_cgroup is also applied.)

I think this routine is enough generic to be enhanced for hierarchy in future.
I think move_account() routine can be used for other purpose.
(for example, move_task.)


==
int mem_cgroup_move_account(struct page *page, struct page_cgroup *pc,
struct mem_cgroup *from, struct mem_cgroup *to)
{
struct mem_cgroup_per_zone *from_mz, *to_mz;
int nid, zid;
int ret = 1;

VM_BUG_ON(to->no_limit == 0);
VM_BUG_ON(!irqs_disabled());

nid = page_to_nid(page);
zid = page_zonenum(page);
from_mz = mem_cgroup_zoneinfo(from, nid, zid);
to_mz = mem_cgroup_zoneinfo(to, nid, zid);

if (res_counter_charge(&to->res, PAGE_SIZE)) {
/* Now, we assume no_limit...no failure here. */
return ret;
}

if (spin_trylock(&to_mz->lru_lock)) {
__mem_cgroup_remove_list(from_mz, pc);
css_put(&from->css);
res_counter_uncharge(&from->res, PAGE_SIZE);
pc->mem_cgroup = to;
css_get(&to->css);
__mem_cgroup_add_list(to_mz, pc);
ret = 0;
spin_unlock(&to_mz->lru_lock);
} else {
res_counter_uncharge(&to->res, PAGE_SIZE);
}

return ret;
}
/*
* This routine moves all account to root cgroup.
*/
static void mem_cgroup_force_empty_list(struct mem_cgroup *mem,
struct mem_cgroup_per_zone *mz,
enum lru_list lru)
{
struct page_cgroup *pc;
unsigned long flags;
struct list_head *list;
int drain = 0;

list = &mz->lists[lru];

spin_lock_irqsave(&mz->lru_lock, flags);
while (!list_empty(list)) {
pc = list_entry(list->prev, struct page_cgroup, lru);
if (PcgObsolete(pc)) {
list_move(&pc->lru, list);
/* This page_cgroup may remain on this list until
we drain it. */
if (drain++ > MEMCG_LRU_THRESH/2) {
spin_unlock_irqrestore(&mz->lru_lock, flags);
mem_cgroup_all_force_drain();
yield();
drain = 0;
spin_lock_irqsave(&mz->lru_lock, flags);
}
continue;
}
if (mem_cgroup_move_account(page, pc->page,
mem, &init_mem_cgroup)) {
/* some confliction */
list_move(&pc->lru, list);
spin_unlock_irqrestore(&mz->lru_lock, flags);
yield();
spin_lock_irqsave(&mz->lru_lock, flags);
}
if (atomic_read(&mem->css.cgroup->count) > 0)
break;
}
spin_unlock_irqrestore(&mz->lru_lock, flags);
}
==



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