[ofa-general] Re: IPoIB path caching

[Sean Hefty]

> Indeed. The argument I was trying to make is that arp cache invalidation 
>  requires IPoIB PR cache invalidation, this handles 100% of the cases, 
> including the 10% not covered by doing cache invalidation based only on 
>  IB events such as port up / sm lid change / sm reregister / etc

ARP cache invalidation does not require, nor does it actually do IPoIB 
PR cache invalidation.  We can argue whether or not it should, but the 
two are not linked together today.

The local SA updates paths either in response to an event: LID change, 
port state change, GID in/out of service, etc., or when refreshed via a 
module parameter.  A refresh can occur in response to an administrative 
event, when told to by a system administrator, before executing large 
jobs, periodically based on a timer, or whenever else.  That policy is 
outside the scope of the proposed patches, but covers all other 
potential cases where the cache must be updated.

I like the advantages of keeping the local SA entirely in user space, 
but there are issues that need to be worked through first.  And 
implementation wise, it's unlikely to give us anything that remains in 
sync any better than what's already been proposed without the use of 
non-standard extensions.

- Sean