Re: [PATCH 2/3] mincore: Introduce the MINCORE_ANON bit

[Pavel Emelyanov <xemul@parallels.com>]

On 12/26/2011 08:35 PM, KOSAKI Motohiro wrote:
> 2011/12/26 Pavel Emelyanov <xemul@parallels.com>:
>> On 12/26/2011 04:05 AM, KOSAKI Motohiro wrote:
>>>> +static unsigned char mincore_pte(struct vm_area_struct *vma, unsigned long addr, pte_t pte)
>>>> +{
>>>> +       struct page *pg;
>>>> +
>>>> +       pg = vm_normal_page(vma, addr, pte);
>>>> +       if (!pg)
>>>> +               return 0;
>>>> +       else
>>>> +               return PageAnon(pg) ? MINCORE_ANON : 0;
>>>> +}
>>>> +
>>>
>>> How do your program handle tmpfs pages (and/or ram device pages)?
>>
>> Do you mean mapped files from tmpfs? Currently just any other file.
>> Do you see problems with this patch wrt tmpfs?
> 
> If you don't save mapped file on tmpfs or other volatile devices, the process
> might not restored. The data might already destroyed. 

Yes I know this, thanks :\

> The common strategy are two,
> 
> 1) save all opened file by different ways.
> 2) save all mapped file even though clean file cache.
> 
> In both case, we don't reduce freezed data size. So, I'm interesting
> you strategy.

The tmpfs contents itself is supposed to be preserved, it's not a problem. The problem I'm trying
to solve here is which page from task mappings (i.e. vm_area_struct-s) to save and which not to.

Do the proposed MINCORE_RESIDENT and MINCORE_ANON bits have problems with this from
your POV?

Thanks,
Pavel

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