On 12/12/2014 16:14, Feng Wu wrote:
> + if (irq_remapping_cap(IRQ_POSTING_CAP)) {
> + struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
> + struct pi_desc old, new;
> + unsigned int dest;
> +
> + memset(&old, 0, sizeof(old));
> + memset(&new, 0, sizeof(new));
This is quite expensive. Just use an u64 for old_control and
new_control, instead of a full struct.
>
> + pi_clear_sn(&new);
This can be simply new.sn = 0. It does not need atomic operations.
Same in patch 24 (if needed at all there---see the reply there).
>
> + if (irq_remapping_cap(IRQ_POSTING_CAP)) {
> + struct pi_desc *pi_desc = vcpu_to_pi_desc(vcpu);
> + struct pi_desc old, new;
> +
> + memset(&old, 0, sizeof(old));
> + memset(&new, 0, sizeof(new));
> +
Here you do not need old/new at all because...
> + if (vcpu->preempted) {
> + do {
> + old.control = new.control = pi_desc->control;
> + pi_set_sn(&new);
> + } while (cmpxchg(&pi_desc->control, old.control,
> + new.control) != old.control);
this can do pi_set_sn directly on pi_desc, without the cmpxchg.
Paolo
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