Michael Schnell wrote:
>
> >futex mutexes should be easy. The harder bit is TLS. Switching to
> >NPTL implies both, as far as I know.
> >
> Sorry for my ignorance. What is TLS and what are the implications ? Do
> you have any pointers ? There are several requests for NPTL on
> NIOS-arch. I don't really see the big advantage over old Linux threads,
> but of course it is nice to provide the most recent stuff...
TLS "Thread Local Storage" is the ability to say
int __thread i;
And get a variable which is different in each thread, and fast to
access. You can get a similar effect with standard pthreads and using
macros for every access, but this is better and faster when available.
NPTL's advantages over LinuxThreads which come to mind:
- Faster to create and destroy threads.
- No "manager" extra thread memory overhead.
- Faster to communicate between threads because it doesn't use signals.
- Futex-based primitives mean mutexes and other synchronisation
between threads are much faster.
- You can have inter-process (system-wide) mutexes and other
synchronisation objects in shared memory.
- Actually POSIX correct behaviour. E.g. getpid() returns
the same value for each thread. Signals are delivered in the way
described by POSIX. Etc. So more code just works with NPTL.
- Stopping the whole process with SIGSTOP works properly, and
killing it with SIGKILL works properly.
- ps and top show one process, not lots of processes.
-- Jamie
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