Hi, How may I ask for your help? Now I'm studying the linux scheduler(sched.c). And I'm wondering what likey()/unlikely macros mean. I could find they're defined in linux/compiler.h as follows. /* * Generic compiler-dependent macros required for kernel * build go below this comment. Actual compiler/compiler version * specific implementations come from the above header files */ #define likely(x) __builtin_expect(!!(x), 1) #define unlikely(x) __builtin_expect(!!(x), 0) And I could find __builtin_expect()'s definition only in linux/compiler-gcc2.h as a follow. I don't know what's going if __GNUC_MINOR__ is over 96, though... #if __GNUC_MINOR__ < 96 # define __builtin_expect(x, expected_value) (x) #endif As a result, although it seems likely() and unlikely() do nothing, is my expectation correct? If there are other references about this, please let me know. Regards, Shinpei Kato -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
