On Wed, Dec 17, 2008 at 09:08:04AM +1030, Rusty Russell wrote: > On Tuesday 16 December 2008 17:43:14 David Miller wrote: > > Here ya go: > > Very interesting. There's a little noise there (that first local_inc of 243 > is wrong), but the picture is clear: trivalue is the best implementation for > sparc64. > > Note: trivalue uses 3 values, so instead of hitting random values across 8MB > it's across 24MB, and despite the resulting cache damage it's 15% faster. The > cpu_local_inc test is a single value, so no cache effects: it shows trivalue > to be 3 to 3.5 times faster in the cache-hot case. > > This sucks, because it really does mean that there's no one-size-fits-all > implementation of local_t. There's also no platform yet where atomic_long_t > is the right choice; and that's the default! > > Any chance of an IA64 or s390 run? You can normalize if you like, since > it's only to compare the different approaches. atomic_long_t seems to be the right choice on s390. IRQ disable/enable is expensive, but the compare and swap instruction is cheap. I just gave it a quick shot, but please note that there were two hypervisors running below my system (add_return is missing since I used your first patch): atomic_long 19 18 - 3 17 irqsave/rest 57 58 - 39 22 trivalue 43 43 - 4 45 local_t 18 20 - 2 16 -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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