linux-kernel - Re: [PATCH 1/2] [RFC] Range tree implementation

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Date:	Tue, 20 Mar 2012 11:04:03 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Dmitry Adamushko <dmitry.adamushko@...il.com>
CC:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Android Kernel Team <kernel-team@...roid.com>,
	Robert Love <rlove@...gle.com>, Mel Gorman <mel@....ul.ie>,
	Hugh Dickins <hughd@...gle.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Rik van Riel <riel@...hat.com>,
	Dave Chinner <david@...morbit.com>, Neil Brown <neilb@...e.de>,
	Andrea Righi <andrea@...terlinux.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: [PATCH 1/2] [RFC] Range tree implementation

On 03/20/2012 03:00 AM, Dmitry Adamushko wrote:
> Hi John,
>
> On 16 March 2012 23:51, John Stultz<john.stultz@...aro.org>  wrote:
>> After Andrew suggested something like his mumbletree idea
>> to better store a list of ranges, I worked on a few different
>> approaches, and this is what I've finally managed to get working.
>>
>> I suspect range-tree isn't a totally accurate name, but I
>> couldn't quite make out the difference between range trees
>> and interval trees, so I just picked one to call it. Do
>> let me know if you have a better name.
>>
>> The idea of storing ranges in a tree is nice, but has a number
>> of complications. When adding a range, its possible that a
>> large range will consume and merge a number of smaller ranges.
> Have you considered using 'prio_tree' (include/linux/prio_tree.h)? If
> we aim at addressing a wide range of possible use-cases (different
> patterns of adding/removing volatile ranges), then, at first glance,
> prio_tree looks like a better approach.
I'll take a closer look at that!

> e.g. for the "consume and merge a number of smaller ranges" scenario
> above, prio_tree gives O(log n) [ O(log n + m) ] behavior iso O(m log
> n) in your case.
Yea, one of the items I was looking at yesterday was to improve the 
range insert/remove usage, since I end up starting each lookup from the 
root node over and over.  I'm thinking of adding a iterate-next type 
call so that we don't re-start the lookup each iteration of the loop 
once we've found an item.

Thanks again for the great feedback!

-john

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