Re : .... get_page_from_freelist : MInority Suggestion to accept GFP_NOFAIL accept during boot

[Mitchell Erblich]

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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