Simon Burge wrote:

> Here's results for a couple of MIPS cpus:
> 
> bcm1250 (mips64 500MHz)
> 
>         syscall lock:		time= 7.174320
>         RAS lock:		time= 0.220124
>         test-and-set lock:	time= 0.450196
> 
> au1000 (mips32 396MHz)
>  
>         syscall lock:		time=12.292677
>         RAS lock:		time= 0.227705
>         test-and-set lock:	time= 0.531112
>  
> r4400 (mips3 120MHz)
>  
>         syscall lock:		time=48.880966
>         RAS lock:		time= 1.048473
>         test-and-set lock:	time= 1.090512

Great!  I suspected it would be good on mips.  Maybe all
register argument-passing CPUs.

> So RAS is faster in all cases.  I'm thinking of something like:
> 
> 	if sysctl(hw.ncpus == 1) {
> 		RAS lock
> 	} else {
> 		if (sysctl(machdep.llsc) {
> 			test-and-set lock
> 		} else {
> 			/* Eek!  SMP without ll/sc */
> 			syscall lock
> 		}
> 	}

Yeah.  This is what I did in the pthread library.

Thanks for the good news, Simon.

	-- Gregory McGarry <g.mcgarry@ieee.org>