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Message-ID: <4F6BC166.80407@jp.fujitsu.com>
Date: Fri, 23 Mar 2012 09:18:46 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: "linux-mm@...ck.org" <linux-mm@...ck.org>,
Linux Kernel <linux-kernel@...r.kernel.org>,
"cgroups@...r.kernel.org" <cgroups@...r.kernel.org>,
Hugh Dickins <hughd@...gle.com>,
"n-horiguchi@...jp.nec.com" <n-horiguchi@...jp.nec.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...e.cz>,
Glauber Costa <glommer@...allels.com>
Subject: Re: [PATCH] memcg: change behavior of moving charges at task move
(2012/03/23 6:36), Andrew Morton wrote:
> On Wed, 21 Mar 2012 18:52:04 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@...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
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