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Date:   Tue, 8 Dec 2020 08:59:42 +0000 (UTC)
From:   Christoph Lameter <cl@linux.com>
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To:     Mark Haywood <mark.haywood@oracle.com>
cc:     =?ISO-8859-15?Q?H=E5kon_Bugge?= <haakon.bugge@oracle.com>,
        Honggang LI <honli@redhat.com>, Jason Gunthorpe <jgg@ziepe.ca>,
        OFED mailing list <linux-rdma@vger.kernel.org>
Subject: Re: Is there a working cache for path record and lids etc for
 librdmacm?
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On Mon, 7 Dec 2020, Mark Haywood wrote:

> On 12/7/20 5:28 AM, Christoph Lameter wrote:
> > Looking at librdmacm/rdma_getaddrinfo():
> >
> > It seems that the call to the IBACM via ucma_ib_resolve() is only done
> > after a regular getaddrinfo() was run. Is IBACM truly able to provide
> > address resolution or is it just some strange after processing if the main
> > resolution attempt fails?
>
>
>
> getaddrinfo() is called only if 'node' or 'service' are set. Otherwise,
> 'hints' are set and used.

Right. It calls the function that does an RPC to ibacm *after*
getaddrinfo. This is confusing. I would have expected this to happen
*before* getaddrinfo and that getaddrinfo would be skipped if ibacm
returns a hit in the cache.

If node is set then we want something to be resolved. So it *first* should
check with ibacm. No?

> ucma_set_ib_route() (called from rdma_resolve_route()) calls
> rdma_getaddrinfo() with 'hints' set.

That in turn calls getaddrinfo.

> Increasing the ibacm log level and then using cmtime(1), I see log messages
> that indicate that ibacm is resolving addresses.

Well it does that under certain circumstances. What kind of addresses are
you resolving?