From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759350Ab2GMAdN (ORCPT ); Thu, 12 Jul 2012 20:33:13 -0400 Received: from mail-gh0-f174.google.com ([209.85.160.174]:42733 "EHLO mail-gh0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933656Ab2GMAdG (ORCPT ); Thu, 12 Jul 2012 20:33:06 -0400 From: Michel Lespinasse To: aarcange@redhat.com, dwmw2@infradead.org, riel@redhat.com, peterz@infradead.org, daniel.santos@pobox.com, axboe@kernel.dk, ebiederm@xmission.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org Subject: [PATCH v2 10/12] rbtree: optimize case selection logic in __rb_erase_color() Date: Thu, 12 Jul 2012 17:31:55 -0700 Message-Id: <1342139517-3451-11-git-send-email-walken@google.com> X-Mailer: git-send-email 1.7.7.3 In-Reply-To: <1342139517-3451-1-git-send-email-walken@google.com> References: <1342139517-3451-1-git-send-email-walken@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org In __rb_erase_color(), we have to select one of 3 cases depending on the color on the 'other' node children. If both children are black, we flip a few node colors and iterate. Otherwise, we do either one or two tree rotations, depending on the color of the 'other' child opposite to 'node', and then we are done. The corresponding logic had duplicate checks for the color of the 'other' child opposite to 'node'. It was checking it first to determine if both children are black, and then to determine how many tree rotations are required. Rearrange the logic to avoid that extra check. Signed-off-by: Michel Lespinasse --- lib/rbtree.c | 68 +++++++++++++++++++++++++-------------------------------- 1 files changed, 30 insertions(+), 38 deletions(-) diff --git a/lib/rbtree.c b/lib/rbtree.c index baf7c83..eb823a3 100644 --- a/lib/rbtree.c +++ b/lib/rbtree.c @@ -283,28 +283,24 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent, __rb_rotate_left(parent, root); other = parent->rb_right; } - if ((!other->rb_left || rb_is_black(other->rb_left)) && - (!other->rb_right || rb_is_black(other->rb_right))) - { - rb_set_red(other); - node = parent; - parent = rb_parent(node); - } - else - { - if (!other->rb_right || rb_is_black(other->rb_right)) - { - rb_set_black(other->rb_left); + if (!other->rb_right || rb_is_black(other->rb_right)) { + if (!other->rb_left || + rb_is_black(other->rb_left)) { rb_set_red(other); - __rb_rotate_right(other, root); - other = parent->rb_right; + node = parent; + parent = rb_parent(node); + continue; } - rb_set_color(other, rb_color(parent)); - rb_set_black(parent); - rb_set_black(other->rb_right); - __rb_rotate_left(parent, root); - break; + rb_set_black(other->rb_left); + rb_set_red(other); + __rb_rotate_right(other, root); + other = parent->rb_right; } + rb_set_color(other, rb_color(parent)); + rb_set_black(parent); + rb_set_black(other->rb_right); + __rb_rotate_left(parent, root); + break; } else { other = parent->rb_left; if (rb_is_red(other)) @@ -314,28 +310,24 @@ static void __rb_erase_color(struct rb_node *node, struct rb_node *parent, __rb_rotate_right(parent, root); other = parent->rb_left; } - if ((!other->rb_left || rb_is_black(other->rb_left)) && - (!other->rb_right || rb_is_black(other->rb_right))) - { - rb_set_red(other); - node = parent; - parent = rb_parent(node); - } - else - { - if (!other->rb_left || rb_is_black(other->rb_left)) - { - rb_set_black(other->rb_right); + if (!other->rb_left || rb_is_black(other->rb_left)) { + if (!other->rb_right || + rb_is_black(other->rb_right)) { rb_set_red(other); - __rb_rotate_left(other, root); - other = parent->rb_left; + node = parent; + parent = rb_parent(node); + continue; } - rb_set_color(other, rb_color(parent)); - rb_set_black(parent); - rb_set_black(other->rb_left); - __rb_rotate_right(parent, root); - break; + rb_set_black(other->rb_right); + rb_set_red(other); + __rb_rotate_left(other, root); + other = parent->rb_left; } + rb_set_color(other, rb_color(parent)); + rb_set_black(parent); + rb_set_black(other->rb_left); + __rb_rotate_right(parent, root); + break; } } } -- 1.7.7.3