On Wednesday 11 June 2008 03:42:15 Christoph Lameter wrote: > 1. The x86 implementation does not exist because the segment register has > so far not been available on x86_64. So you could not do the solution. > You need the zero basing. Then you can use per_xxx_add in cpu_inc. Yes: for 64 bit x86, getting rid of the PDA or zero-basing is required. > 2. The general solution created overhead that is often not needed. If we > would have done vm event counters with local_t then we would have > atomic overhead for each increment on f.e. IA64. That was not > acceptable. cpu_alloc never falls back to atomic operations. You can implement it either way. I've said that three times now. The current generic one uses atomics, but preempt disable/enable is possible. > 3. local_t is based on the atomic logic. But percpu handling is > fundamentally different in that accesses without the special macros > are okay provided you are in a non preemptible or irq context! > A local_t declaration makes such accesses impossible. Again, untrue. The interface is already there. So feel free to implement __cpu_local_inc et al in terms of preempt enable and disable so it doesn't need to use atomics. > 4. The modeling of local_t on atomic_t limits it to 32bit! Again wrong. And adding an exclamation mark doesn't make it true. Rusty. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
