On Mon, 19 Nov 2007, David Miller wrote: > Although we have a per-cpu area base in a fixed global register > for addressing, the above isn't beneficial on sparc64 because > the atomic is much slower than doing a: > > local_irq_disable(); > nonatomic_percpu_memory_op(); > local_irq_enable(); > > local_irq_{disable,enable}() together is about 18 cycles. > Just the cmpxchg() part of the atomic sequence is at least > 32 cycles and requires a loop: > > while (1) { > x = ld(); > if (cmpxchg(x, op(x))) > break; > } > > which bloats up the atomic version even more.
In that case the generic fallbacks can just provide what you already have. - 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/