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bench: add routing next-hop microbench

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Measures the per-forwarded-packet cost of routing candidate assembly
(routing_candidates over a synthetic RoutingView) against a zero-alloc
reference across 8/32/128/256 peers, with per-call allocation counts via
a counting allocator. Criterion harness; no production code change.
This commit is contained in:
Johnathan Corgan
2026-07-11 01:48:34 +00:00
parent 2cffc10520
commit 8aab71af86
2 changed files with 370 additions and 0 deletions
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5
Cargo.toml
View File

@@ -109,3 +109,8 @@ path = "src/bin/fips-gateway.rs"
[[bin]]
name = "fipstop"
path = "src/bin/fipstop/main.rs"
[[bench]]
name = "routing_next_hop"
path = "benches/routing_next_hop.rs"
harness = false

365
benches/routing_next_hop.rs Normal file
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@@ -0,0 +1,365 @@
//! Micro-benchmark quantifying the per-forwarded-packet heap-allocation cost
//! of the routing next-hop candidate-assembly path.
//!
//! `find_next_hop` runs once per forwarded data packet. Its sans-IO core
//! assembles a `Vec<Candidate>` by enumerating every peer through the
//! `RoutingView` seam: `peer_addrs()` materializes a `Vec<NodeAddr>` of all
//! peers, the survivors are snapshotted (each cloning its `TreeCoordinate`),
//! and the result is collected into a second `Vec`. This bench measures that
//! per-call allocation against a fused zero-alloc reference that iterates the
//! peer map directly and borrows coordinates instead of cloning.
//!
//! Visibility caveat: the production `routing_candidates` / `select_best_candidate`
//! / `RoutingView` / `Candidate` are `pub(crate)` (src/proto/routing/core.rs)
//! and are not re-exported at the crate root, so an external bench crate cannot
//! name them. Rather than change production visibility, this file reproduces
//! that path verbatim over the real public `NodeAddr` / `TreeCoordinate` /
//! `CoordEntry` / `BloomFilter` types with the same iterator chain and the same
//! `HashMap`-backed view the shell uses (src/node/mod.rs NodeRoutingView). The
//! allocation behavior is therefore identical to production by construction;
//! only the symbol identity differs.
use std::alloc::{GlobalAlloc, Layout, System};
use std::collections::HashMap;
use std::hint::black_box;
use std::sync::atomic::{AtomicUsize, Ordering};
use criterion::{BenchmarkId, Criterion, criterion_group, criterion_main};
use fips::{BloomFilter, NodeAddr, TreeCoordinate};
// ---------------------------------------------------------------------------
// Counting global allocator: bumps a process-global counter on every heap
// allocation operation (alloc / alloc_zeroed / realloc). Sampled tightly and
// single-threaded in `report_allocs` so no unrelated allocations are captured.
// ---------------------------------------------------------------------------
struct CountingAlloc;
static ALLOCS: AtomicUsize = AtomicUsize::new(0);
unsafe impl GlobalAlloc for CountingAlloc {
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
ALLOCS.fetch_add(1, Ordering::Relaxed);
unsafe { System.alloc(layout) }
}
unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
unsafe { System.dealloc(ptr, layout) }
}
unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
ALLOCS.fetch_add(1, Ordering::Relaxed);
unsafe { System.alloc_zeroed(layout) }
}
unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
ALLOCS.fetch_add(1, Ordering::Relaxed);
unsafe { System.realloc(ptr, layout, new_size) }
}
}
#[global_allocator]
static GLOBAL: CountingAlloc = CountingAlloc;
const PEER_COUNTS: [usize; 4] = [8, 32, 128, 256];
/// Fraction of peers whose bloom filter reports the destination reachable.
const REACH_NUMERATOR: usize = 1;
const REACH_DENOMINATOR: usize = 2;
/// Tree depth for synthetic coordinates (self..root), a realistic mesh depth.
const COORD_DEPTH: usize = 8;
// ---------------------------------------------------------------------------
// Reproduction of the pub(crate) routing seam (src/proto/routing/core.rs).
// ---------------------------------------------------------------------------
trait RoutingView {
fn peer_addrs(&self) -> Vec<NodeAddr>;
fn peer_may_reach(&self, peer: &NodeAddr, dest: &NodeAddr) -> bool;
fn peer_can_send(&self, peer: &NodeAddr) -> bool;
fn peer_link_cost(&self, peer: &NodeAddr) -> f64;
fn peer_coords(&self, peer: &NodeAddr) -> Option<TreeCoordinate>;
}
struct Candidate {
addr: NodeAddr,
can_send: bool,
link_cost: f64,
coords: Option<TreeCoordinate>,
}
/// Verbatim from `routing::routing_candidates` (core.rs). Allocates the
/// `peer_addrs` Vec, clones each survivor's coords, and collects into a Vec.
fn routing_candidates(rv: &impl RoutingView, dest: &NodeAddr) -> Vec<Candidate> {
rv.peer_addrs()
.into_iter()
.filter(|peer| rv.peer_may_reach(peer, dest))
.map(|peer| Candidate {
can_send: rv.peer_can_send(&peer),
link_cost: rv.peer_link_cost(&peer),
coords: rv.peer_coords(&peer),
addr: peer,
})
.collect()
}
/// Verbatim from `routing::select_best_candidate` (core.rs). Pure, no alloc.
fn select_best_candidate(
candidates: &[Candidate],
dest_coords: &TreeCoordinate,
my_coords: &TreeCoordinate,
) -> Option<NodeAddr> {
let my_distance = my_coords.distance_to(dest_coords);
let mut best: Option<(&Candidate, f64, usize)> = None;
for candidate in candidates {
if !candidate.can_send {
continue;
}
let cost = candidate.link_cost;
let dist = candidate
.coords
.as_ref()
.map(|pc| pc.distance_to(dest_coords))
.unwrap_or(usize::MAX);
if dist >= my_distance {
continue;
}
let dominated = match &best {
None => true,
Some((_, best_cost, best_dist)) => {
cost < *best_cost
|| (cost == *best_cost && dist < *best_dist)
|| (cost == *best_cost
&& dist == *best_dist
&& candidate.addr < best.as_ref().unwrap().0.addr)
}
};
if dominated {
best = Some((candidate, cost, dist));
}
}
best.map(|(candidate, _, _)| candidate.addr)
}
// ---------------------------------------------------------------------------
// Bench-local view, HashMap-backed exactly like src/node/mod.rs NodeRoutingView.
// ---------------------------------------------------------------------------
struct BenchPeer {
bloom: BloomFilter,
can_send: bool,
link_cost: f64,
}
struct BenchView {
peers: HashMap<NodeAddr, BenchPeer>,
coords: HashMap<NodeAddr, TreeCoordinate>,
}
impl RoutingView for BenchView {
fn peer_addrs(&self) -> Vec<NodeAddr> {
self.peers.keys().copied().collect()
}
fn peer_may_reach(&self, peer: &NodeAddr, dest: &NodeAddr) -> bool {
self.peers.get(peer).is_some_and(|p| p.bloom.contains(dest))
}
fn peer_can_send(&self, peer: &NodeAddr) -> bool {
self.peers.get(peer).is_some_and(|p| p.can_send)
}
fn peer_link_cost(&self, peer: &NodeAddr) -> f64 {
self.peers.get(peer).map_or(f64::INFINITY, |p| p.link_cost)
}
fn peer_coords(&self, peer: &NodeAddr) -> Option<TreeCoordinate> {
self.coords.get(peer).cloned()
}
}
/// Zero-alloc reference: what an iterator/visitor seam would do. Iterates the
/// peer map directly, fuses the may_reach + can_send filters, borrows coords
/// instead of cloning, and tracks the best hop inline. No Vec, no coord clone.
fn resolve_next_hop_zeroalloc(
view: &BenchView,
dest: &NodeAddr,
dest_coords: &TreeCoordinate,
my_coords: &TreeCoordinate,
) -> Option<NodeAddr> {
let my_distance = my_coords.distance_to(dest_coords);
let mut best: Option<(NodeAddr, f64, usize)> = None;
for (addr, peer) in &view.peers {
if !peer.bloom.contains(dest) {
continue;
}
if !peer.can_send {
continue;
}
let cost = peer.link_cost;
let dist = view
.coords
.get(addr)
.map(|pc| pc.distance_to(dest_coords))
.unwrap_or(usize::MAX);
if dist >= my_distance {
continue;
}
let dominated = match &best {
None => true,
Some((best_addr, best_cost, best_dist)) => {
cost < *best_cost
|| (cost == *best_cost && dist < *best_dist)
|| (cost == *best_cost && dist == *best_dist && *addr < *best_addr)
}
};
if dominated {
best = Some((*addr, cost, dist));
}
}
best.map(|(addr, _, _)| addr)
}
// ---------------------------------------------------------------------------
// Scenario construction.
// ---------------------------------------------------------------------------
fn addr(tag: u8, i: u16) -> NodeAddr {
let mut b = [0u8; 16];
b[0] = tag;
b[1..3].copy_from_slice(&i.to_le_bytes());
NodeAddr::from_bytes(b)
}
/// A depth-`COORD_DEPTH` coordinate whose leaf is `leaf`, sharing a fixed
/// interior path and root with `shared_tag`. Peers built with the dest's
/// shared_tag sit close to the destination (distance 2); a distinct shared_tag
/// sits far (near the root), modeling our own position.
fn coord(leaf: NodeAddr, shared_tag: u8) -> TreeCoordinate {
let mut path = Vec::with_capacity(COORD_DEPTH);
path.push(leaf);
for level in 1..(COORD_DEPTH - 1) {
path.push(addr(shared_tag, level as u16));
}
path.push(addr(9, 0)); // common root
TreeCoordinate::from_addrs(path).expect("valid coord path")
}
struct Scenario {
view: BenchView,
dest: NodeAddr,
dest_coords: TreeCoordinate,
my_coords: TreeCoordinate,
}
impl Scenario {
fn new(n: usize) -> Self {
let dest = addr(2, 0);
// Destination path uses interior tag 4; peers reuse tag 4 so survivors
// are close to the destination. Our own coords use tag 5 (far).
let dest_coords = coord(dest, 4);
let my_coords = coord(addr(6, 0), 5);
let mut peers = HashMap::new();
let mut coords = HashMap::new();
for i in 0..n {
let paddr = addr(1, i as u16);
let mut bloom = BloomFilter::new();
// Realistic fill: a handful of unrelated reachable addrs.
for f in 0..4u16 {
bloom.insert(&addr(7, i as u16 * 4 + f));
}
// A controlled fraction advertise the destination as reachable.
if (i % REACH_DENOMINATOR) < REACH_NUMERATOR {
bloom.insert(&dest);
}
peers.insert(
paddr,
BenchPeer {
bloom,
can_send: true,
link_cost: 1.0 + (i as f64) * 0.01,
},
);
// Peers share the destination's interior path (tag 4) → close.
coords.insert(paddr, coord(paddr, 4));
}
Self {
view: BenchView { peers, coords },
dest,
dest_coords,
my_coords,
}
}
fn survivors(&self) -> usize {
self.view
.peers
.values()
.filter(|p| p.bloom.contains(&self.dest))
.count()
}
}
// ---------------------------------------------------------------------------
// Allocation-per-call report (printed once, before criterion timing).
// ---------------------------------------------------------------------------
fn count_allocs<T>(iters: usize, mut f: impl FnMut() -> T) -> f64 {
for _ in 0..8 {
black_box(f());
}
let start = ALLOCS.load(Ordering::Relaxed);
for _ in 0..iters {
black_box(f());
}
let end = ALLOCS.load(Ordering::Relaxed);
(end - start) as f64 / iters as f64
}
fn report_allocs() {
const ITERS: usize = 2000;
println!("\n=== allocations per call (heap alloc ops: alloc+alloc_zeroed+realloc) ===");
println!(
"{:>6} {:>10} {:>16} {:>16}",
"peers", "survivors", "current/call", "zero-alloc/call"
);
for &n in &PEER_COUNTS {
let s = Scenario::new(n);
let survivors = s.survivors();
let current = count_allocs(ITERS, || {
let cands = routing_candidates(&s.view, &s.dest);
select_best_candidate(&cands, &s.dest_coords, &s.my_coords)
});
let zero = count_allocs(ITERS, || {
resolve_next_hop_zeroalloc(&s.view, &s.dest, &s.dest_coords, &s.my_coords)
});
println!("{n:>6} {survivors:>10} {current:>16.2} {zero:>16.2}");
}
println!();
}
fn bench_next_hop(c: &mut Criterion) {
report_allocs();
let mut group = c.benchmark_group("find_next_hop");
for &n in &PEER_COUNTS {
let scenario = Scenario::new(n);
group.bench_with_input(BenchmarkId::new("current_alloc", n), &n, |b, _| {
b.iter(|| {
let cands = routing_candidates(&scenario.view, &scenario.dest);
black_box(select_best_candidate(
&cands,
&scenario.dest_coords,
&scenario.my_coords,
))
});
});
group.bench_with_input(BenchmarkId::new("zero_alloc_ref", n), &n, |b, _| {
b.iter(|| {
black_box(resolve_next_hop_zeroalloc(
&scenario.view,
&scenario.dest,
&scenario.dest_coords,
&scenario.my_coords,
))
});
});
}
group.finish();
}
criterion_group! {
name = benches;
config = Criterion::default().sample_size(50);
targets = bench_next_hop
}
criterion_main!(benches);