Re: atomic-up.h speedup : compared with irq disable/enable

Hello.

Mathieu Desnoyers wrote:
> Some more information about the non LOCKed atomic ops that I now use on SMP :

> A test ran on a 3GHz Pentium 4 shows that (20000 loops) :

> irq save/restore pair      210.60 ns
> 
> cmpxchg                     49.46 ns
>     (76 % speedup)
> cmpxchg-up (no lock prefix)  9.00 ns
>     (95 % speedup)

> Does anyone still believe that cli()/sti() is faster ? :)

    Alas, it's not so for RISCs anyway -- they don't have RMW type 
instructions with memory desctinations, so you still have to use cli/sti (or 
locking).
   I guess we also need to benchmark this on some RISCs like ARM/MIPS/PPC...

> Mathieu

WBR, Sergei