linux-kernel - Re: [PATCH RFC 2/3] proc/smaps: show amount of nonlinear ptes in vma

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Message-ID: <CAHGf_=qh1eogM2cywMrJnhHtcbW9gav4Ktb8inYJmar2wG4j=Q@mail.gmail.com>
Date:	Tue, 1 May 2012 14:08:59 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH RFC 2/3] proc/smaps: show amount of nonlinear ptes in vma

On Tue, May 1, 2012 at 1:56 PM, Konstantin Khlebnikov
<khlebnikov@...nvz.org> wrote:
> KOSAKI Motohiro wrote:
>>
>> On Mon, Apr 30, 2012 at 7:29 AM, Konstantin Khlebnikov
>> <khlebnikov@...nvz.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@...nvz.org>
>>> Requested-by: Pavel Emelyanov<xemul@...allels.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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