lagg/lacp poor traffic distribution

[Fabien Thomas]

On Dec 21, 2010, at 3:00 PM, Eugene Grosbein wrote:

> On 21.12.2010 19:11, Fabien Thomas wrote:
> 
>>>> I had this problem with igb driver, and I found, that lagg selects
>>>> outgoing interface based on packet header flowid field if M_FLOWID field
>>>> is set. And in the igb driver code flowid is set as 
>>>> 
>>>> #if __FreeBSD_version >= 800000
>>>> <------><------><------>rxr->fmp->m_pkthdr.flowid = que->msix;
>>>> <------><------><------>rxr->fmp->m_flags |= M_FLOWID;
>>>> #endif
>>>> 
>>>> The same thing in em driver with MULTIQUEUE 
>>>> 
>>>> That does not give enough number of flows to balance traffic well, so I
>>>> commented check in if_lagg.c
>>>> 
>>>> lagg_lb_start(struct lagg_softc *sc, struct mbuf *m)
>>>> {
>>>> <------>struct lagg_lb *lb = (struct lagg_lb *)sc->sc_psc;
>>>> <------>struct lagg_port *lp = NULL;
>>>> <------>uint32_t p = 0;
>>>> 
>>>> //<---->if (m->m_flags & M_FLOWID)
>>>> //<----><------>p = m->m_pkthdr.flowid;
>>>> //<---->else
>>>> 
>>>> and with this change I have much better load distribution across interfaces.
>>>> 
>>>> Hope it helps.
>>> 
>>> You are perfectly right. By disabling flow usage I've obtained load sharing
>>> close to even (final patch follows). Two questions:
>>> 
>>> 1. Is it a bug or design problem?
>> 
>> How many queues have you with igb? If it's one it will explain why the flowid is bad for load balancing with lagg.
> 
> How do I know? I've read igb(4) manual page and found no words
vmstat -i will show the queue (intr for the queue) normally it's the number of CPU available.



> about queues within igb, nor I have any knowledge about them.
> 
>> The problem is that flowid is good if the number of queue is = or a multiple of the number of lagg ports.
> 
> Now I see, thanks.
> 
> Eugene Grosbein