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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 29 of 66] don't alloc harder for gfp nomemalloc even if nowait
Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, Marcelo Tosatti <mtosatti@redhat.com>,
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        Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
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        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Ingo Molnar <mingo@elte.hu>, Mike Travis <travis@sgi.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Christoph Lameter <cl@linux-foundation.org>,
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> From: Andrea Arcangeli <aarcange@redhat.com>
> 
> Not worth throwing away the precious reserved free memory pool for allocations
> that can fail gracefully (either through mempool or because they're transhuge
> allocations later falling back to 4k allocations).
> 
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> Acked-by: Rik van Riel <riel@redhat.com>
> ---
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1941,7 +1941,12 @@ gfp_to_alloc_flags(gfp_t gfp_mask)
>  	alloc_flags |= (__force int) (gfp_mask & __GFP_HIGH);
>  
>  	if (!wait) {
> -		alloc_flags |= ALLOC_HARDER;
> +		/*
> +		 * Not worth trying to allocate harder for
> +		 * __GFP_NOMEMALLOC even if it can't schedule.
> +		 */
> +		if  (!(gfp_mask & __GFP_NOMEMALLOC))
> +			alloc_flags |= ALLOC_HARDER;
>  		/*
>  		 * Ignore cpuset if GFP_ATOMIC (!wait) rather than fail alloc.
>  		 * See also cpuset_zone_allowed() comment in kernel/cpuset.c.

I like this.
	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>