Rayhaan JaufeerallyandClaude Fable 5.1
c70a223d0d
A router with many peers has a reader of the table's journal for each session that is sent learned routes, seventy on ddln, and every change to the table wakes them all. Each pass of a reader went round every shard, and for each shard took a count on the table (an Arc clone) to hold it while the shard was read, and gave it back after: two atomic adds on one cache line, by seventy readers, 256 shards a pass. A profile of ddln taking a table from the other router had the reader's poll as the top function at two to three cores, and in the Linux VM with 64 such sessions half of all CPU time was in the two atomic add instructions. The sessions writing to the table waited behind it: the table came in at 58,000 routes a second. The count is now taken once a poll. And each journal keeps its latest sequence number in an atomic the table holds the other end of, so that a reader can tell a shard with nothing new for it from one with something without the shard's lock, and pass over it: on a quiet table, which is what the readers see most of the time, a pass is a load a shard and no lock. An exporter that is sent little of a table, as one to a peer at an exchange is, no longer makes a verdict of nothing for a prefix the peer does not hold, which cost a map insert and a lookup on the way out, and tells a route that came down or across (RFC 9234) from its attributes' bytes before parsing them. Testing: the mesh benchmark can have any number of collector sessions of the first router (BENCH_COLLECTORS): peers in the sense of RFC 9234, sent learned routes, with the feeders' routes marked as having come across from a peer, so that each has a reader following the table while it fills and passes nearly all of it over, as a router with many peers at exchanges has. In the Linux VM with 64 of them, three rounds alternating with the previous commit, the routers' exchange of their tables takes 11 s instead of 20 s, at 86 s of CPU time instead of 155 s; without them it is unchanged. The table's tests, the server tests, the integration tests, the kernel tests and every lab phase pass. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>