Re: Is there a working cache for path record and lids etc for librdmacm?

[Honggang LI <honli@redhat.com>]

On Tue, Nov 24, 2020 at 07:01:25PM +0000, Christopher Lameter wrote:
> On Mon, 23 Nov 2020, Håkon Bugge wrote:
> 
> > > Got version 33.0 from Redhat with the option. Set it but ibacm still times
> > > out when trying to contact the SM.
> >
> > Contact the peer ibacm, that is. Is it started?
> 
> 
> It can contact the peer ibacm if its running on a particular host. Then
> the resolution succeeds. But we want ibacm to talk to the subnet manager.
> 
> > And, ib_acme bypasses the kernel_only check. I assume a real app (e.g.,
> > qperf <destination_ip> -cm1 rc_bw) would work, but incur an excess delay
> > due to the ibacm timeout, before failing back to the kernel neighbour
> > cache.
> 
> Ok. But what does it matter?
> 
> 
> How do I figure out why ibacm is not talking to the subnet manager?

No, you can't talking to subnet manager, if you resolve IPoIB IP address
or hostname to PathRecord. The query MAD packets will be send to one
multicast group all ibacm service attached.

To resolve IPoIB address to PathRecord, you must:
1) The IPoIB interface must UP and RUNNING on the client and target
side.
2) The ibacm service must RUNNING on the client and target.

Thanks