linux-kernel - Re: [PATCH 1/4] mm: Add __GFP_NO_OOM

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Date:	Sun, 3 May 2009 19:54:50 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, pavel@....cz,
	torvalds@...ux-foundation.org, jens.axboe@...cle.com,
	alan-jenkins@...fmail.co.uk, linux-kernel@...r.kernel.org,
	kernel-testers@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH 1/4] mm: Add __GFP_NO_OOM_KILL flag

On Sun, May 03, 2009 at 02:22:06AM +0200, Rafael J. Wysocki wrote:
> From: Andrew Morton <akpm@...ux-foundation.org>
> 
> > > Remind me: why can't we just allocate N pages at suspend-time?
> > 
> > We need half of memory free. The reason we can't "just allocate" is
> > probably OOM killer; but my memories are quite weak :-(.
> 
> hm.  You'd think that with our splendid range of __GFP_foo falgs, there
> would be some combo which would suit this requirement but I can't
> immediately spot one.
> 
> We can always add another I guess.  Something like...
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> ---
>  include/linux/gfp.h |    3 ++-
>  mm/page_alloc.c     |    3 ++-
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> Index: linux-2.6/mm/page_alloc.c
> ===================================================================
> --- linux-2.6.orig/mm/page_alloc.c
> +++ linux-2.6/mm/page_alloc.c
> @@ -1620,7 +1620,8 @@ nofail_alloc:
>  		}
>  
>  		/* The OOM killer will not help higher order allocs so fail */
> -		if (order > PAGE_ALLOC_COSTLY_ORDER) {
> +		if (order > PAGE_ALLOC_COSTLY_ORDER ||
> +				(gfp_mask & __GFP_NO_OOM_KILL)) {
>  			clear_zonelist_oom(zonelist, gfp_mask);
>  			goto nopage;
>  		}
> Index: linux-2.6/include/linux/gfp.h
> ===================================================================
> --- linux-2.6.orig/include/linux/gfp.h
> +++ linux-2.6/include/linux/gfp.h
> @@ -51,8 +51,9 @@ struct vm_area_struct;
>  #define __GFP_THISNODE	((__force gfp_t)0x40000u)/* No fallback, no policies */
>  #define __GFP_RECLAIMABLE ((__force gfp_t)0x80000u) /* Page is reclaimable */
>  #define __GFP_MOVABLE	((__force gfp_t)0x100000u)  /* Page is movable */
> +#define __GFP_NO_OOM_KILL ((__force gfp_t)0x200000u)  /* Don't invoke out_of_memory() */
>  
> -#define __GFP_BITS_SHIFT 21	/* Room for 21 __GFP_FOO bits */
> +#define __GFP_BITS_SHIFT 22	/* Number of__GFP_FOO bits */
                                            ^ missed a white space :)
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