Hello,
Somebody can tell me an example of using locking mechanism based on futex? (for muticore x86 CPU, CentOS)
Thanks Dima
+3
A:
Pthreads' mutexes are implemented using futexes on recent versions of Linux. Pthreads is the standard C threading API on Linux, and is part of the Posix standard, so you can easily port your program to other Unix-like systems. You should avoid using futexes directly unless you have very unusual needs, because they're very hard to use correctly - use pthreads, or a higher-level, language-specific API (which will almost certainly use pthreads itself).
Doug
2010-09-24 13:08:52
What about latest version of CentOS 5.5? Is Pthreads' mutexes on CentOS 5.5 are implemented using futexes?Thanks
Dima
2010-09-24 14:53:54
Futexes have been used by pthreads on all distributions of Linux since about 2004, when 2.6-series kernels were adopted. That includes CentOS. I don't understand why you need to worry about them, though... they're largely an implementation detail.
Doug
2010-09-24 15:51:07
because I need to use locks in very time-critical path of the server application (the place where all data passed through).I think that is better to use some "fast" locking mechanism...
Dima
2010-09-24 19:23:25
@Dima: You shouldn't assume that pthreads mutexes are too slow until you've tried them. And futexes aren't really a complete locking mechanism, they're just the kernel part of it. You still need to write some assembly language in order to use them as a lock, which is very, very hard to get right. I recommend writing your program with pthreads mutexes, which actually are very fast. If your program is too slow, then try making the locks finer-grained, so that different threads don't need all need to use the same lock at the same time. Although this sounds hard, it's easier than using futexes.
Doug
2010-09-25 02:05:07