linux-kernel - Re: [patch 3/4] mm: bootmem: drop superfluous range check when freeing pages in bulk

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Date:	Tue, 13 Dec 2011 16:28:43 +0100
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 3/4] mm: bootmem: drop superfluous range check when
 freeing pages in bulk

Hello Johannes,

On Tue, Dec 13, 2011 at 02:58:30PM +0100, Johannes Weiner wrote:
> The area node_bootmem_map represents is aligned to BITS_PER_LONG, and
> all bits in any aligned word of that map valid.  When the represented
> area extends beyond the end of the node, the non-existant pages will
> be marked as reserved.
> 
> As a result, when freeing a page block, doing an explicit range check
> for whether that block is within the node's range is redundant as the
> bitmap is consulted anyway to see whether all pages in the block are
> unreserved.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
I suggest to drop my patch then and add something like

	Reported-by: $me

to this one instead.

Other than that I will give your series a spin on my ARM machine later
today.

Best regards
Uwe

> ---
>  mm/bootmem.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/bootmem.c b/mm/bootmem.c
> index 3e6f152..1aea171 100644
> --- a/mm/bootmem.c
> +++ b/mm/bootmem.c
> @@ -197,7 +197,7 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata)
>  		idx = start - bdata->node_min_pfn;
>  		vec = ~map[idx / BITS_PER_LONG];
>  
> -		if (aligned && vec == ~0UL && start + BITS_PER_LONG <= end) {
> +		if (aligned && vec == ~0UL) {
>  			int order = ilog2(BITS_PER_LONG);
>  
>  			__free_pages_bootmem(pfn_to_page(start), order);
> -- 
> 1.7.7.3
> 
> 

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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