bgp_rib::table::RibTable holds every route from every peer and the best
one for each prefix. It is not used by the server yet; this adds it with
its tests and benchmarks.
- Organised by prefix. A row holds the prefix's routes from all peers in
one array; choosing again after a change reads that row and nothing else.
- A route is sixteen bytes: a pointer to its attribute set and one word
holding the peer and the first three steps of selection (LOCAL_PREF, AS
path length, ORIGIN) as a single number. That number alone settles most
changes; a tie goes on to MED, compared only within a neighbouring AS
and in a way that does not depend on arrival order, and the tie-breaks.
- Attribute sets are stored once, in wire form, with what selection needs
from them worked out when they are stored.
- Sharded by hash of the prefix, a lock per shard. A session applies its
own UPDATEs; there is no queue or owning thread in front of the table.
- Readers take one shard at a time for reading and look at rows in place.
Route selection is checked against a plain implementation with no
shortcuts by a property test over random announcements, withdrawals and
session flaps, for both the chosen route and the count of changes.
On a RIPE RIS dump from AMS-IX (148 peers, 39.3 million routes), against
the Adj-RIB-In actor, which does no selection:
actor table
memory 11.0 GiB 1.8 GiB (279 -> 48 bytes a route)
load, 1 thread 10.2 s 12.3 s
load, 12 threads (no gain) 2.1 s (19 million routes a second)
read every route 1.6 s, copying 8 GiB, table stopped
0.2 s, in place, table running
The benchmark crate counts memory only with --features count-memory: the
counters are shared between threads and distort the timings.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
crates/bench reads TABLE_DUMP_V2 dumps (RFC 6396) as published by RIPE RIS
and RouteViews, and `--bench real_table` runs the Adj-RIB-In on one. The
dumps are not checked in; crates/bench/data/README.md says how to fetch
one. Without a dump the benchmark says so and does nothing.
It also prints what in the table decides the cost of a RIB: routes per
prefix, distinct attribute sets, how many routes share a set, and how much
the sets are shared between peers.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
crates/bench makes a synthetic full table (a million IPv4 and 230,000 IPv6
prefixes, announced by several peers in UPDATEs shaped like a router's)
and times the steps of taking it in: decoding, the Adj-RIB-In, snapshot,
peer removal, and the whole path over TCP. It also counts the memory the
table holds, and fills a plain packed hash map with the same routes as a
point of comparison.
Run with `cargo bench -p bgp-bench`.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
