On Fri, Dec 08, 2006 at 09:06:00AM -0800, Christoph Lameter wrote: > On Fri, 8 Dec 2006, David Howells wrote: > > > > It is the most universal atomic instruction that I know of. > > > > I think TAS-type things and XCHG-type things are more common. > > Huh? The most popular architectures are i386 x86_64 sparc ia64 etc which > all have one or the other form of cmpxchg (some issues with early sparc > and i386).
According to the latest figures, 621 million ARM processors were shipped in Q3, which equates to about 78 processors per second. (taken from http://www.arm.com/news/15300.html). I'd like to know the figures for these other so-called "popular architectures". But in any case that's an utterly irrelevant point to the argument at hand. > > In fact I think more things have LL/SC than have CMPXCHG. > > LL/SC can be easily used to come up with a cmpxchg equivalent. As proven previously the reverse is also true. And as shown previously the cheaper out of the two for all platforms is the LL/SC based implementation, where the architecture specific implementation can be _either_ LL/SC based or cmpxchg based depending on what is supported in their hardware. I'm going to keep saying this until people get it. -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
