I don't know enough myself about the different gc algorithms to make a suggestion. All I could offer is a wish-list of what we'd like Arc gc to be able to do, which perhaps you might find useful if you went to an algorithms forum or mailing list and found out what gc algorithms might be able to do that.
I'm not able to look at your source code because your copyright notice (it looks like maybe it came from a template?) says "all right reserved" without a notice of the code being released under an open source license. If your code is derived from Arc then you may need to release it under the Perl Artistic Licence (the same as Arc); or, if it's not, but you'd like to release it under an open source license, then the MIT License (http://opensource.org/licenses/mit-license) is a good choice to consider.
It's right since the header files are all created in Xcode 4 with the default template. I will make it under an open source license after reading both licenses. Thank you for the advices!
