Subject: Re: [boost] [fiber] new version in vault
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2009-11-30 12:48:21
Helge Bahmann wrote:
> why would you ever want to use a mutex that does not properly inform the
> system scheduler until when the calling thread should be suspended (in
> case of contention) for "true" inter-thread (or even inter-process)
> coordination?
When you believe that the probability of contention is very small, and
you care only about average and not worst-case performance, and you
wish to avoid the overhead (e.g. time or code or data size) of
"properly informing" the system scheduler.
Earlier in this thread, Stefan Strasser wrote:
> a mutex template with a parameter on what to do to waste some time (this_fiber::yield,
> this_thread::yield, spinning...) could clean this up
Yes. I implemented something like this that could either spin, or call
sched_yield, or (on Linux) call futex_wait. It's basically a
Futex-based mutex that implements the other behaviours by replacing the
futex with something trivial. See
http://svn.chezphil.org/libpbe/trunk/include/Mutex.hh and Futex.hh,
Yield.hh, Spin.hh in the same directory. I've discussed the relative
performance of these things on this list in the past.
Regards, Phil.