Re: [PATCH] memcg: change behavior of moving charges at task move

KAMEZAWA Hiroyuki
2012-03-23T00:20:36Z

(2012/03/23 6:36), Andrew Morton wrote:

> On Wed, 21 Mar 2012 18:52:04 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
>> static struct page *mc_handle_swap_pte(struct vm_area_struct *vma,
>> unsigned long addr, pte_t ptent, swp_entry_t *entry)
>> {
>> - int usage_count;
>> struct page *page = NULL;
>> swp_entry_t ent = pte_to_swp_entry(ptent);
>>
>> if (!move_anon() || non_swap_entry(ent))
>> return NULL;
>> - usage_count = mem_cgroup_count_swap_user(ent, &page);
>> - if (usage_count > 1) { /* we don't move shared anon */
>> - if (page)
>> - put_page(page);
>> - return NULL;
>> - }
>> +#ifdef CONFIG_SWAP
>> + /*
>> + * Avoid lookup_swap_cache() not to update statistics.
>> + */
>
> I don't understand this comment - what is it trying to tell us?
>

High Dickins advised me to use find_get_page() rather than lookup_swap_cache()
because lookup_swap_cache() has some statistics with swap.

>> + page = find_get_page(&swapper_space, ent.val);
>
> The code won't even compile if CONFIG_SWAP=n?
>

mm/built-in.o: In function `mc_handle_swap_pte':
/home/kamezawa/Kernel/next/linux/mm/memcontrol.c:5172: undefined reference to `swapper_space'
make: *** [.tmp_vmlinux1] Error 1

Ah...but I think this function (mc_handle_swap_pte) itself should be under CONFIG_SWAP.
I'll post v2.

Thank you for review!
-Kame