threading and multicores, pros and cons

[John Nagle]

Paul Rubin wrote:
> John Nagle <nagle at animats.com> writes:
> 
>>    If locking is expensive on x86, it's implemented wrong.
>>It's done right in QNX, with inline code for the non-blocking case.
> 
> 
> Acquiring the lock still takes an expensive instruction, LOCK XCHG or
> whatever.  I think QNX is usually run on embedded cpu's with less
> extensive caching as these multicore x86's, so the lock prefix may be
> less expensive in the QNX systems.

     That's not so bad.  See

http://lists.freebsd.org/pipermail/freebsd-current/2004-August/033462.html

     But there are dumb thread implementations that make
a system call for every lock.

					John Nagle