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

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Message-ID: <20111213154432.GE1818@cmpxchg.org>
Date:	Tue, 13 Dec 2011 16:44:32 +0100
From:	Johannes Weiner <hannes@...xchg.org>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
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

On Tue, Dec 13, 2011 at 04:28:43PM +0100, Uwe Kleine-König wrote:
> 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.

Your patch is a real and obvious fix, while mine is just a cleanup but
has more obscure dependencies on how the bitmap is managed.

If you don't mind, I would prefer to keep them as separate changes.

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

Thanks a lot!
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