[ovs-dev] OVS_LIKELY in miniflow_extract()

[Jarno Rajahalme]

On May 29, 2014, at 2:09 PM, Ben Pfaff <blp at nicira.com> wrote:

> On Thu, May 29, 2014 at 01:56:31PM -0700, Jarno Rajahalme wrote:
>> 
>>> 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.
> 
> OK.
> 
> Your patch or mine?

I don’t have one, so… also as I took it overboard, it might be better you fix it to your liking, less expected back and forth.

  Jarno

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