Claudio Martella commented on GIRAPH-45:
I'm not sure whether sending messages in a streamy way would actually diminish
any kind of memory pressure. As messages need the current superstep to be
finished before they can be consumed, i guess this would just transfer the
pressure to the other nodes where they are transfered to. In a certain
scenario, this can actually mean putting more pressure on the "cumulative
memory" consumed (the total memory of the nodes in the cluster).
Suppose vertex A sends a message to vertex B, C, D and E. B and C are on the
same node as A, D is on another second node and E is on a third node. This
means that B and C share the message sent by A as they live in the same JVM
(forget about a semantic where the message needs to be cloned before they are
sent). In this scenario we would have #nodes copies of the same message overall
the cluster. Topology-based graph partitioning would allow these messages to be
sent mostly to vertices living in the same JVM (supposing the communication
pattern of vertices follows graph topology) and would alleviate this problem.
It feels like keeping messages out-of-core is the best option we have right now
and if we manage to save the messages in the same order vertices they are sent
to are processed, we could even get a scan-based computation that would grant
quite a throughput. Does it make sense?
> Improve the way to keep outgoing messages
> Key: GIRAPH-45
> URL: https://issues.apache.org/jira/browse/GIRAPH-45
> Project: Giraph
> Issue Type: Improvement
> Components: bsp
> Reporter: Hyunsik Choi
> Assignee: Hyunsik Choi
> As discussed in GIRAPH-12(http://goo.gl/CE32U), I think that there is a
> potential problem to cause out of memory when the rate of message generation
> is higher than the rate of message flush (or network bandwidth).
> To overcome this problem, we need more eager strategy for message flushing or
> some approach to spill messages into disk.
> The below link is Dmitriy's suggestion.
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