linux-kernel - Re: [PATCH 1/2] mm: Introduce GFP_PANIC for early-boot allocations

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Message-ID: <4A054AB5.1000601@cs.helsinki.fi>
Date:	Sat, 09 May 2009 12:19:49 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Andrew Morton <akpm@...ux-foundation.org>, gorcunov@...nvz.org,
	kosaki.motohiro@...fujitsu.com, mel@....ul.ie,
	cl@...ux-foundation.org, riel@...hat.com,
	linux-kernel@...r.kernel.org, rientjes@...gle.com
Subject: Re: [PATCH 1/2] mm: Introduce GFP_PANIC for early-boot allocations

Ingo Molnar wrote:
> * Pekka Enberg <penberg@...helsinki.fi> wrote:
> 
>> Hi Andrew,
>>
>> Andrew Morton wrote:
>>> On Fri, 08 May 2009 18:10:28 +0300
>>> Pekka Enberg <penberg@...helsinki.fi> wrote:
>>>
>>>> +#define GFP_PANIC	(__GFP_NOFAIL | __GFP_NORETRY)
>>> urgh, you have to be kidding me.  This significantly worsens complexity
>>> and risk in core MM and it's just yuk.
>>>
>>> I think we can justify pulling such dopey party tricks to save 
>>> pageframe space, or bits in page.flags and such.  But just to 
>>> save a scrap of memory which would have been released during boot 
>>> anwyay?  Don't think so.
>> No, I wasn't kidding and I don't agree that it "significantly 
>> worsens complexity". The point is not to save memory but to 
>> clearly annotate those special call-sites that really don't need 
>> to check for out-of-memory.
> 
> Frankly, i cannot believe that so many smart people dont see the 
> simple, universal, un-arguable truism in the following statement:
> 
>  it is shorter, tidier, more maintainable, more reviewable to write:
> 
> 	ptr = kmalloc(GFP_BOOT, size);
> 
>  than to write:
> 
> 	ptr = kmalloc(GFP_KERNEL, size);
> 	BUG_ON(!ptr);

Hey, that's a much better name! I guess we don't need to support 
GFP_ATOMIC? I'll repost the series with Peter's system_state != BOOTING 
warning. Lets see if that makes the patch more palatable to Andrew.

			Pekka
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