Re: [boost] Re: Lightweight Mutex Code

From: Mattias Flodin (flodin_at_[hidden])
Date: 2004-07-06 02:23:28

Quoting "Aaron W. LaFramboise" <aaronrabiddog51_at_[hidden]>:
> Well, even critical sections, Windows's fastest mutex primative, are
> much slower in the noncontended case than a spinlock.  A two-stage
> method is needed to match the performance of the present spinlock: a
> lightweight atomic operation followed by a heavy-weight mutex if the
> lock is contended.  This is why I was mentioned 8 bytes (one word for
> the critical section, one word for the atomic operation) would be necessary.

I'm quite surprised by this claim. What you describe is precisely how WIN32
critical sections work. If your measures show them to be slower, there must be
some other reason for it. WIN32 also provides
InitializeCriticalSectionAndSpinCount which will cause a busy-wait for a few
cycles before resorting to waiting on the kernel lock.

/Mattias