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

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Date:	Tue, 01 May 2012 21:56:52 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
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

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.
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