Re: 7.1 vs. 7.2 on AIX 5L

Added to TODO:

* Evaluate AIX cs() spinlock macro for performance optimizations (Tatsuo)

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Tatsuo Ishii wrote:
> > > NOTICE:  LockRelease: no such lock
> > > 
> > > I'm afraid now the locking is broken. Will look into more.
> > 
> > Next try would be _check_lock (found in sys/atomic_op.h):
> > 
> > Description (from man page)
> > 
> > The _check_lock subroutine performs an atomic (uninterruptible) sequence of
> > operations. The compare_and_swap subroutine is similar, but does not issue
> > synchronization instructions and therefore is inappropriate for updating lock
> > words.
> > 
> > replace the TAS define with:
> > #define TAS(lock)       _check_lock(lock, 0, 1)
> > 
> > > with LinuxPPC asm:     2m9.340s
> > > with cs:            10m11.15s
> > > with fetch_and_or:    3m55.19s
> > 
> > with _check_lock:        3m29.990s
> > 
> > I think that the culprit may also be the S_UNLOCK (use _clear_lock) ?
> 
> Thanks. I will try with it.
> 
> BTW, I'm still wondering why 7.2 is slower than 7.1 on AIX. Tom said
> cs() is responsible for that. But not only 7.2 but 7.1 uses cs(). It
> seems cs() does not explain the difference of the performance.
> --
> Tatsuo Ishii
> 
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