难怪快了这么多，内存管理也好了，原来用了freebsd7的内存管理，嘿嘿
One of the FreeBSD technologies used by Firefox 3 is the new memory allocator, “jemalloc”, which was written by FreeBSD developer Jason Evans for the FreeBSD 7 operating system. jemalloc is a fast, efficient memory allocator with excellent performance on multiprocessor machines. Though already a part of the FreeBSD 7 operating system, the Mozilla project has chosen to also incorporate it directly inside the Firefox 3 browser to improve memory performance and reduce memory use on other operating systems with legacy memory allocators.