From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx200.postini.com [74.125.245.200]) by kanga.kvack.org (Postfix) with SMTP id B2C676B004D for ; Wed, 21 Dec 2011 19:17:11 -0500 (EST) Date: Thu, 22 Dec 2011 11:17:07 +1100 From: Dave Chinner Subject: Re: [PATCH] radix_tree: expand comment on optimization Message-ID: <20111222001707.GI23662@dastard> References: <20111221050740.GD23662@dastard> <20111221221527.GE23662@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins Cc: Andrew Morton , Jan Kara , Mel Gorman , linux-kernel@vger.kernel.org, linux-mm@kvack.org On Wed, Dec 21, 2011 at 03:57:16PM -0800, Hugh Dickins wrote: > Expand comment on optimization in radix_tree_range_tag_if_tagged(), > along the lines proposed by Dave Chinner. > > Signed-off-by: Hugh Dickins > --- > And with -p2, this patch will also apply to the rtth tree. > > lib/radix-tree.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > --- mmotm/lib/radix-tree.c 2011-12-16 20:40:26.152758485 -0800 > +++ linux/lib/radix-tree.c 2011-12-21 14:57:20.073657540 -0800 > @@ -703,7 +703,13 @@ unsigned long radix_tree_range_tag_if_ta > node = node->parent; > } > > - /* optimization: no need to walk up from this node again */ > + /* > + * Small optimization: now clear that node pointer. > + * Since all of this slot's ancestors now have the tag set > + * from setting it above, we have no further need to walk > + * back up the tree setting tags, until we update slot to > + * point to another radix_tree_node. > + */ > node = NULL; Looks good. I might remember why it was done now ;) Cheers, Dave. -- Dave Chinner david@fromorbit.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org