[openib-general] re RDS missing features

[Ranjit Pandit]

On 5/2/06, Or Gerlitz <ogerlitz at voltaire.com> wrote:
> Ranjit Pandit wrote:
> > Yes.
> > There is no issue. It's just next in line for me to implement.
>
> So what's remained to implement? if the app attempt to send data to
> 127.0.0.1 or a local IPoIB address then you are opening a connection to
> this address over the CMA and in the passive "side" you just do
> rdma_listen without binding to any device. In other words, no change on
> the active side and a simplification of the passive side to support
> this. Do i miss something here?

Loopback connections can be optimized by not going to the HCA.
In b-copy mode we can directly copy sends into destination sockets on
the same node.

>
> >> +2 by failover, are you referring to APM? that is failover between IB
> >> pathes to/from the same HCA
> >> over which the original connection/QP was established or you are talking
> >> on failover between HCAs
> >
> > Failover within and across HCAs. APM does not work for failover across
> > HCAs.
>
> I see. Can you remind me ... where is the location of the reference gen1
>   RDS code? does it support failover?

Yes, Rds reference implementation implements failover across HCAs.
It was checked into contrib/silverstorm/rds.
r3471 was the first checkin and then a few more updates were made with
bug fixes.

>
> Also, for within the HCA failover, are you talking on APM or basically,
> you apply the same failover scheme between to ports no matter if they
> are on on the same HCA or on different HCAs?

Keep it simple ie., apply the same failover scheme between two ports
whether on same HCA or not.

>
> Are you aware to something in the openib infrastructure which is missing
> for the failover design of RDS? if you specify the design/requirements i
> am sure people on this list can quickly say if something is missing...
>
For failover Rds need support for the following:
1. Ability to assign single IP address to multiple IB ports
2. Address resolution mechanism should return multiple paths for the
same destination IP address.

On SilverStorm stack a single IP address can be assigned to two ports
in the system.
When a path fails, RDS can re-establish connection to the same
destination IP address...ipoib_path( dst_ip) returns all possible
paths to the destination ip.

Does the CMA handle multiple paths to a destination IP?
It does not need to return multiple paths to Rds. For now, even if it
picks the first
available path that should be sufficient.

> Or.
>
> >> [openfabrics-ewg] Before we can start testing - we needto ensure that
> >> RDS is fully ported.
> >>
> >> Pandit, Ranjit rpandit at silverstorm.com
> >>
> >> Following features are yet to be implemented in OpenFabric Rds:
> >>
> >>  1.     Failover
> >> 2.      Loopback connections
> >> 3.      support for /proc fs like Rds config, stats and info.
> >>
> >>
> >>
> >> Ranjit
>
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