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SubjectRe : .... get_page_from_freelist : MInority Suggestion to accept GFP_NOFAIL accept during boot
Date
Group,

Make plain text so vger.kernel.org will accept this..

Mitchell Erblich
====================

On Jul 6, 2009, at 4:56 PM, Mitchell Erblich wrote:

> David,
>
> The web page http://lkml.indiana.edu/hypermail/linux/kernel/
>
> Looking at the thread of emails on June 24 at 11:07:23
> upcoming kerneloops.org item: get_page_from_freelist
>
> We have code from Arjan de Van
>
> it's this warning in mm/page_alloc.c:
>
> * __GFP_NOFAIL is not to be used in new code.
> *
> * All __GFP_NOFAIL callers should be fixed so that they
> * properly detect and handle allocation failures.
> *
> * We most definitely don't want callers attempting to
> * allocate greater than single-page units with
> * __GFP_NOFAIL.
> */
> WARN_ON_ONCE(order > 0);
>
>
> Mitchell Erblich
> ======================
>
> On Jul 3, 2009, at 2:01 AM, David Rientjes wrote:
>
>> On Thu, 2 Jul 2009, Mitchell Erblich wrote:
>>
>>> Group,
>>>
>>>
>>> If I may suggest a minority opinion about the depreciating of the
>>> GFP_NOFAIL flag..
>>>
>>> I saw no discussion on the acceptance of using this flag during
>>> boot
>>> and shortly
>>> after boot.
>>>
>>> Many kernel structures require memory and thus should guarantee
>>> memory
>>> before they continue.
>>>
>>> As Linux is moved within embedded environments with smaller
>>> amounts of
>>> physical memory, the chance that earlier mem failures becomes
>>> higher.
>>>
>>> For this logic alone, my minority opinion is to not depreciate the
>>> GFP_NOFAIL flag.
>>>
>>
>> I'm confused by your request because all allocations with orders
>> under
>> PAGE_ALLOC_COSTLY_ORDER are inherently __GFP_NOFAIL and those that
>> are not
>> can easily implement the same behavior in the caller:
>>
>> struct page *page;
>> do {
>> page = alloc_pages(...);
>> } while (!page);
>>
>> Hopefully something could be done to ensure the next call to
>> alloc_pages()
>> would be more likely to succeed, but __GFP_NOFAIL doesn't provide
>> that
>> anyway.
>



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