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From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Date: Tue, 1 May 2012 14:08:59 -0400
Message-ID: <CAHGf_=qh1eogM2cywMrJnhHtcbW9gav4Ktb8inYJmar2wG4j=Q@mail.gmail.com>
Subject: Re: [PATCH RFC 2/3] proc/smaps: show amount of nonlinear ptes in vma
To: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
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On Tue, May 1, 2012 at 1:56 PM, Konstantin Khlebnikov
<khlebnikov@openvz.org> wrote:
> KOSAKI Motohiro wrote:
>>
>> On Mon, Apr 30, 2012 at 7:29 AM, Konstantin Khlebnikov
>> <khlebnikov@openvz.org> ?wrote:
>>>
>>> Currently, nonlinear mappings can not be distinguished from ordinary
>>> mappings.
>>> This patch adds into /proc/pid/smaps line "Nonlinear:<size> ?kB", where
>>> size is
>>> amount of nonlinear ptes in vma, this line appears only if VM_NONLINEAR
>>> is set.
>>> This information may be useful not only for checkpoint/restore project.
>>>
>>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@openvz.org>
>>> Requested-by: Pavel Emelyanov<xemul@parallels.com>
>>> ---
>>> ?fs/proc/task_mmu.c | ? 12 ++++++++++++
>>> ?1 file changed, 12 insertions(+)
>>>
>>> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
>>> index acee5fd..b1d9729 100644
>>> --- a/fs/proc/task_mmu.c
>>> +++ b/fs/proc/task_mmu.c
>>> @@ -393,6 +393,7 @@ struct mem_size_stats {
>>> ? ? ? ?unsigned long anonymous;
>>> ? ? ? ?unsigned long anonymous_thp;
>>> ? ? ? ?unsigned long swap;
>>> + ? ? ? unsigned long nonlinear;
>>> ? ? ? ?u64 pss;
>>> ?};
>>>
>>> @@ -402,6 +403,7 @@ static void smaps_pte_entry(pte_t ptent, unsigned
>>> long addr,
>>> ?{
>>> ? ? ? ?struct mem_size_stats *mss = walk->private;
>>> ? ? ? ?struct vm_area_struct *vma = mss->vma;
>>> + ? ? ? pgoff_t pgoff = linear_page_index(vma, addr);
>>> ? ? ? ?struct page *page = NULL;
>>> ? ? ? ?int mapcount;
>>>
>>> @@ -414,6 +416,9 @@ static void smaps_pte_entry(pte_t ptent, unsigned
>>> long addr,
>>> ? ? ? ? ? ? ? ? ? ? ? ?mss->swap += ptent_size;
>>> ? ? ? ? ? ? ? ?else if (is_migration_entry(swpent))
>>> ? ? ? ? ? ? ? ? ? ? ? ?page = migration_entry_to_page(swpent);
>>> + ? ? ? } else if (pte_file(ptent)) {
>>> + ? ? ? ? ? ? ? if (pte_to_pgoff(ptent) != pgoff)
>>> + ? ? ? ? ? ? ? ? ? ? ? mss->nonlinear += ptent_size;
>>
>>
>> I think this is not equal to our non linear mapping definition. Even if
>> pgoff is equal to linear mapping case, it is non linear. I.e. nonlinear is
>> vma attribute. Why do you want to introduce different definition?
>
> VMA attribute can be determined via presence of this field,
> without VM_NONLINEAR it does not appears.

I meant, is there any worth?
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