[ovs-dev] OVS_LIKELY in miniflow_extract()

[Jarno Rajahalme]

> On May 29, 2014, at 1:03 PM, Ben Pfaff <blp at nicira.com> wrote:
> 
> I think that miniflow_extract() goes a little overboard on the
> OVS_LIKELYs.  In particular these seem suspicious:
> 
>            if (OVS_LIKELY((nw_proto != IPPROTO_HOPOPTS)
>        if (OVS_LIKELY(nw_proto == IPPROTO_TCP)) {
>        } else if (OVS_LIKELY(nw_proto == IPPROTO_UDP)) {
>        } else if (OVS_LIKELY(nw_proto == IPPROTO_SCTP)) {
>        } else if (OVS_LIKELY(nw_proto == IPPROTO_ICMP)) {
>        } else if (OVS_LIKELY(nw_proto == IPPROTO_ICMPV6)) {
> 
> I would put all of these into a single outermost OVS_LIKELY, to make
> it easier to read:
>            if (OVS_LIKELY(arp) && OVS_LIKELY(arp->ar_hrd == htons(1))
>                && OVS_LIKELY(arp->ar_pro == htons(ETH_TYPE_IP))
>                && OVS_LIKELY(arp->ar_hln == ETH_ADDR_LEN)
>                && OVS_LIKELY(arp->ar_pln == 4)) {
> 
> What do you think?

You are LIKELY right, and we can always tune these if there is a practical difference in generated code.

  Jarno