Optimize memory usage of CNode::setAddrKnown #6066
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Concept ACK. |
For when you need to keep track of the last N items you've seen, and can tolerate some false-positives.
Use a probabilistic bloom filter to keep track of which addresses we think we have given our peers, instead of a list. This uses much less memory, at the cost of sometimes failing to relay an address to a peer-- worst case if the bloom filter happens to be as full as it gets, 1-in-1,000. Measured memory usage of a full mruset setAddrKnown: 650Kbytes Constant memory usage of CRollingBloomFilter addrKnown: 37Kbytes. This will also help heap fragmentation, because the 37K of storage is allocated when a CNode is created (when a connection to a peer is established) and then there is no per-item-remembered memory allocation. I plan on testing by restarting a full node with an empty peers.dat, running a while with -debug=addrman and -debug=net, and making sure that the 'addr' message traffic out is reasonable. (suggestions for better tests welcome)
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Changed the first commit to pick @sipa 's nit (replace array of 2 pointers to bloom filters with plain-old private members that are initialized in the constructor; less code is better). |
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Tested ACK |
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Concept ACK |
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Closing as #6064 includes this |
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The first pull implements a "rolling bloom filter" class that keeps track of at least the last N elements added (but has a false positive rate when queried whether an element has been added).
The second uses that class to optimize the memory usage of CNode::setAddrKnown, to a fixed 37K of memory per CNode (from about 650K before any changes, or ~300K after @sipa 's #6064 ).