prio_tree: remove

After both prio_tree users have been converted to use red-black trees,
there is no need to keep around the prio tree library anymore.

Signed-off-by: Michel Lespinasse <walken@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 0 insertions, 107 deletions

diff --git a/Documentation/prio_tree.txt b/Documentation/prio_tree.txt
deleted file mode 100644
index 3aa68f9a117b..000000000000
--- a/Documentation/prio_tree.txt
+++ /dev/null
@@ -1,107 +0,0 @@
-The prio_tree.c code indexes vmas using 3 different indexes:
-	* heap_index  = vm_pgoff + vm_size_in_pages : end_vm_pgoff
-	* radix_index = vm_pgoff : start_vm_pgoff
-	* size_index = vm_size_in_pages
-
-A regular radix-priority-search-tree indexes vmas using only heap_index and
-radix_index. The conditions for indexing are:
-	* ->heap_index >= ->left->heap_index &&
-		->heap_index >= ->right->heap_index
-	* if (->heap_index == ->left->heap_index)
-		then ->radix_index < ->left->radix_index;
-	* if (->heap_index == ->right->heap_index)
-		then ->radix_index < ->right->radix_index;
-	* nodes are hashed to left or right subtree using radix_index
-	  similar to a pure binary radix tree.
-
-A regular radix-priority-search-tree helps to store and query
-intervals (vmas). However, a regular radix-priority-search-tree is only
-suitable for storing vmas with different radix indices (vm_pgoff).
-
-Therefore, the prio_tree.c extends the regular radix-priority-search-tree
-to handle many vmas with the same vm_pgoff. Such vmas are handled in
-2 different ways: 1) All vmas with the same radix _and_ heap indices are
-linked using vm_set.list, 2) if there are many vmas with the same radix
-index, but different heap indices and if the regular radix-priority-search
-tree cannot index them all, we build an overflow-sub-tree that indexes such
-vmas using heap and size indices instead of heap and radix indices. For
-example, in the figure below some vmas with vm_pgoff = 0 (zero) are
-indexed by regular radix-priority-search-tree whereas others are pushed
-into an overflow-subtree. Note that all vmas in an overflow-sub-tree have
-the same vm_pgoff (radix_index) and if necessary we build different
-overflow-sub-trees to handle each possible radix_index. For example,
-in figure we have 3 overflow-sub-trees corresponding to radix indices
-0, 2, and 4.
-
-In the final tree the first few (prio_tree_root->index_bits) levels
-are indexed using heap and radix indices whereas the overflow-sub-trees below
-those levels (i.e. levels prio_tree_root->index_bits + 1 and higher) are
-indexed using heap and size indices. In overflow-sub-trees the size_index
-is used for hashing the nodes to appropriate places.
-
-Now, an example prio_tree:
-
-  vmas are represented [radix_index, size_index, heap_index]
-                 i.e., [start_vm_pgoff, vm_size_in_pages, end_vm_pgoff]
-
-level  prio_tree_root->index_bits = 3
------
-												_
-  0			 				[0,7,7]					 |
-  							/     \					 |
-				      ------------------       ------------			 |     Regular
-  				     /					   \			 |  radix priority
-  1		 		[1,6,7]					  [4,3,7]		 |   search tree
-  				/     \					  /     \		 |
-			 -------       -----			    ------       -----		 |  heap-and-radix
-			/		    \			   /		      \		 |      indexed
-  2		    [0,6,6]	 	   [2,5,7]		[5,2,7]		    [6,1,7]	 |
-		    /     \		   /     \		/     \		    /     \	 |
-  3		[0,5,5]	[1,5,6]		[2,4,6]	[3,4,7]	    [4,2,6] [5,1,6]	[6,0,6]	[7,0,7]	 |
-		   /			   /		       /		   		_
-                  /		          /		      /					_
-  4	      [0,4,4]		      [2,3,5]		   [4,1,5]				 |
-  		 /			 /		      /					 |
-  5	     [0,3,3]		     [2,2,4]		  [4,0,4]				 |  Overflow-sub-trees
-  		/			/							 |
-  6	    [0,2,2]		    [2,1,3]							 |    heap-and-size
-  	       /		       /							 |       indexed
-  7	   [0,1,1]		   [2,0,2]							 |
-  	      /											 |
-  8	  [0,0,0]										 |
-  												_
-
-Note that we use prio_tree_root->index_bits to optimize the height
-of the heap-and-radix indexed tree. Since prio_tree_root->index_bits is
-set according to the maximum end_vm_pgoff mapped, we are sure that all
-bits (in vm_pgoff) above prio_tree_root->index_bits are 0 (zero). Therefore,
-we only use the first prio_tree_root->index_bits as radix_index.
-Whenever index_bits is increased in prio_tree_expand, we shuffle the tree
-to make sure that the first prio_tree_root->index_bits levels of the tree
-is indexed properly using heap and radix indices.
-
-We do not optimize the height of overflow-sub-trees using index_bits.
-The reason is: there can be many such overflow-sub-trees and all of
-them have to be suffled whenever the index_bits increases. This may involve
-walking the whole prio_tree in prio_tree_insert->prio_tree_expand code
-path which is not desirable. Hence, we do not optimize the height of the
-heap-and-size indexed overflow-sub-trees using prio_tree->index_bits.
-Instead the overflow sub-trees are indexed using full BITS_PER_LONG bits
-of size_index. This may lead to skewed sub-trees because most of the
-higher significant bits of the size_index are likely to be 0 (zero). In
-the example above, all 3 overflow-sub-trees are skewed. This may marginally
-affect the performance. However, processes rarely map many vmas with the
-same start_vm_pgoff but different end_vm_pgoffs. Therefore, we normally
-do not require overflow-sub-trees to index all vmas.
-
-From the above discussion it is clear that the maximum height of
-a prio_tree can be prio_tree_root->index_bits + BITS_PER_LONG.
-However, in most of the common cases we do not need overflow-sub-trees,
-so the tree height in the common cases will be prio_tree_root->index_bits.
-
-It is fair to mention here that the prio_tree_root->index_bits
-is increased on demand, however, the index_bits is not decreased when
-vmas are removed from the prio_tree. That's tricky to do. Hence, it's
-left as a home work problem.
-
-