]> git.karo-electronics.de Git - karo-tx-linux.git/commit
rbtree: optimize case selection logic in __rb_erase_color()
authorMichel Lespinasse <walken@google.com>
Thu, 13 Sep 2012 00:58:49 +0000 (10:58 +1000)
committerStephen Rothwell <sfr@canb.auug.org.au>
Thu, 13 Sep 2012 07:27:55 +0000 (17:27 +1000)
commite64cbffe030ce3456f78bdd6f78de36017dabd3e
tree6a0b054fe155f94a07fc13ef846ffe46a0d10042
parent1264a7c796702135349fb7d7ed4aefd1c32d6fec
rbtree: optimize case selection logic in __rb_erase_color()

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 <walken@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: David Woodhouse <David.Woodhouse@intel.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Daniel Santos <daniel.santos@pobox.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
lib/rbtree.c