On Fri, Jan 14, 2011 at 07:15:35PM +0900, KAMEZAWA Hiroyuki wrote:
>
> Now, when THP is enabled, memcg's rmdir() function is broken
> because move_account() for THP page is not supported.
>
> This will cause account leak or -EBUSY issue at rmdir().
> This patch fixes the issue by supporting move_account() THP pages.
>
> And account information will be moved to its parent at rmdir().
>
> How to test:
> 79 mount -t cgroup none /cgroup/memory/ -o memory
> 80 mkdir /cgroup/A/
> 81 mkdir /cgroup/memory/A
> 82 mkdir /cgroup/memory/A/B
> 83 cgexec -g memory:A/B ./malloc 128 &
> 84 grep anon /cgroup/memory/A/B/memory.stat
> 85 grep rss /cgroup/memory/A/B/memory.stat
> 86 echo 1728 > /cgroup/memory/A/tasks
> 87 grep rss /cgroup/memory/A/memory.stat
> 88 rmdir /cgroup/memory/A/B/
> 89 grep rss /cgroup/memory/A/memory.stat
>
> - Create 2 level directory and exec a task calls malloc(big chunk).
> - Move a task somewhere (its parent cgroup in above)
> - rmdir /A/B
> - check memory.stat in /A/B is moved to /A after rmdir. and confirm
> RSS/LRU information includes usages it was charged against /A/B.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
> ---
> mm/memcontrol.c | 32 ++++++++++++++++++++++----------
> 1 file changed, 22 insertions(+), 10 deletions(-)
>
> Index: mmotm-0107/mm/memcontrol.c
> ===================================================================
> --- mmotm-0107.orig/mm/memcontrol.c
> +++ mmotm-0107/mm/memcontrol.c
> @@ -2154,6 +2154,10 @@ void mem_cgroup_split_huge_fixup(struct
> smp_wmb(); /* see __commit_charge() */
> SetPageCgroupUsed(tpc);
> VM_BUG_ON(PageCgroupCache(hpc));
> + /*
> + * Note: if dirty ratio etc..are supported,
> + * other flags may need to be copied.
> + */
That's a good comment, but it should be in the patch that introduces
this function and is a bit unrelated in this one.
> }
> #endif
>
> @@ -2175,8 +2179,11 @@ void mem_cgroup_split_huge_fixup(struct
> */
>
> static void __mem_cgroup_move_account(struct page_cgroup *pc,
> - struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
> + struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge,
> + int charge_size)
> {
> + int pagenum = charge_size >> PAGE_SHIFT;
nr_pages?
> +
> VM_BUG_ON(from == to);
> VM_BUG_ON(PageLRU(pc->page));
> VM_BUG_ON(!page_is_cgroup_locked(pc));
> @@ -2190,14 +2197,14 @@ static void __mem_cgroup_move_account(st
> __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
> preempt_enable();
> }
> - mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -1);
> + mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -pagenum);
> if (uncharge)
> /* This is not "cancel", but cancel_charge does all we need. */
> - mem_cgroup_cancel_charge(from, PAGE_SIZE);
> + mem_cgroup_cancel_charge(from, charge_size);
>
> /* caller should have done css_get */
> pc->mem_cgroup = to;
> - mem_cgroup_charge_statistics(to, PageCgroupCache(pc), 1);
> + mem_cgroup_charge_statistics(to, PageCgroupCache(pc), pagenum);
> /*
> * We charges against "to" which may not have any tasks. Then, "to"
> * can be under rmdir(). But in current implementation, caller of
> @@ -2212,7 +2219,8 @@ static void __mem_cgroup_move_account(st
> * __mem_cgroup_move_account()
> */
> static int mem_cgroup_move_account(struct page_cgroup *pc,
> - struct mem_cgroup *from, struct mem_cgroup *to, bool uncharge)
> + struct mem_cgroup *from, struct mem_cgroup *to,
> + bool uncharge, int charge_size)
> {
> int ret = -EINVAL;
> unsigned long flags;
> @@ -2220,7 +2228,7 @@ static int mem_cgroup_move_account(struc
> lock_page_cgroup(pc);
> if (PageCgroupUsed(pc) && pc->mem_cgroup == from) {
> move_lock_page_cgroup(pc, &flags);
> - __mem_cgroup_move_account(pc, from, to, uncharge);
> + __mem_cgroup_move_account(pc, from, to, uncharge, charge_size);
> move_unlock_page_cgroup(pc, &flags);
> ret = 0;
> }
> @@ -2245,6 +2253,7 @@ static int mem_cgroup_move_parent(struct
> struct cgroup *cg = child->css.cgroup;
> struct cgroup *pcg = cg->parent;
> struct mem_cgroup *parent;
> + int charge_size = PAGE_SIZE;
> int ret;
>
> /* Is ROOT ? */
> @@ -2256,16 +2265,19 @@ static int mem_cgroup_move_parent(struct
> goto out;
> if (isolate_lru_page(page))
> goto put;
> + /* The page is isolated from LRU and we have no race with splitting */
> + if (PageTransHuge(page))
> + charge_size = PAGE_SIZE << compound_order(page);
The same as in the previous patch, compound_order() implicitely
handles order-0 pages and should do the right thing without an extra
check.
The comment is valuable, though!
Nitpicks aside:
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
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