There is no real need for storing bucket attributes locally and we may
save some memory by caching the attributes in one central place.
If this becomes a contention problem, we should reduce the lock load
of the central attribute cache.
Introducing a new omnipotent internal API to just pass route updates
from whatever point wherever we want.
From now on, all the exports should be processed by RT_WALK_EXPORTS
macro, and you can also issue a separate feed-only request to just get a
feed and finish.
The exporters can now also stop and the readers must expect that to
happen and recover. Main tables don't stop, though.
We have now better methods how to measure overall performance
and this obsolete protocol has basically rotten away. If anybody
needs its features, feel free to revive it in future.
To avoid needs for keeping local temporary references for attributes,
now one can use ea_lookup_tmp() to ensure that the attributes are
valid and stored until the task ends. After that, the attributes are
automatically unref'd and also deallocated if needed.
Explicitly marking domains eligible for RCU synchronization. It's then
forbidden to lock these domains in RCU critical section to avoid
possible deadlock.
This commit makes the route chains in the tables atomic. This allows not
only standard exports but also feeds and bulk exports to be processed
without ever locking the table.
Design note: the overall data structures are quite brittle. We're using
RCU read-locks to keep track about readers, and we're indicating ongoing
work on the data structures by prepending a REF_OBSOLETE sentinel node
to make every reader go waiting.
All the operations are intended to stay inside nest/rt-table.c and it
may be even best to further refactor the code to hide the routing table
internal structure inside there. Nobody shall definitely write any
routines manipulating live routes in tables from outside.
This ensures that if somebody passes an event to a loop which
has just started executing, then the event gets picked up. Otherwise
there is a race condition causing stray events pending in queue
but without the ping (because the run actually finishes too fast
to pickup the later events).
