What I have in mind is that IPoIB must not use cached IB path info.
If the IB stack has path caching which is in the default flow of
requesting a path record, it should provide an API (eg flag to the
function through which one does path query) to request a non cached path.
Argh! This was the original design. I believe the current design is a
better approach. The ULP shouldn't care whether the PR is cached or not
- only that it's usable.
The design I was thinking to suggest for IPoIB is to almost always use
this API since this policy makes the implementation consistent with the
decisions made by the network stack neighbour cache
This defeats one of the benefit of caching, which is using a single
GetTable query, versus literally hundreds or thousands of Get queries.
Consider that constant all-to-all communication using IPoIB between 1024
ports, with a 15 minute ARP table timeout would hit the SA with close to
600 queries per second.
I agree with Michael that it would be better for a ULP to invalidate
cache entries.
While I agree that there's the potential for a problem, given that IPoIB
has always cached PRs and no one has reported problems, I think we're
overstating the likelihood of issues occurring in practice. Even the SA
caches the path data -- getting a PR from the SA doesn't provide any
additional guarantees.
- Sean
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