From 02884c15580d1e6d498d7908dfc833094a368144 Mon Sep 17 00:00:00 2001
From: tv <tv@krebsco.de>
Date: Wed, 4 Nov 2026 23:52:09 +0100
Subject: benchmark bridge fast link

---
 src/simtest/bench.rs | 39 ++++++++++++++++++++++-----------------
 1 file changed, 22 insertions(+), 17 deletions(-)

(limited to 'src/simtest/bench.rs')

diff --git a/src/simtest/bench.rs b/src/simtest/bench.rs
index ab1809d..d5ca624 100644
--- a/src/simtest/bench.rs
+++ b/src/simtest/bench.rs
@@ -664,13 +664,16 @@ const BRIDGE_WRITES: usize = 200;
 const BRIDGE_VALUE: usize = 256 * 1024;
 /// A hundred a second.
 const BRIDGE_EVERY: Duration = Duration::from_millis(10);
-/// The slow transport, unless `BENCH_BRIDGE_SLOW_RATE` (MiB/s) and
-/// `BENCH_BRIDGE_SLOW_RTT` (ms) say otherwise.
+/// The fast transport and the slow one, unless `BENCH_BRIDGE_FAST_RATE`,
+/// `BENCH_BRIDGE_SLOW_RATE` (MiB/s) and `BENCH_BRIDGE_FAST_RTT`, `BENCH_BRIDGE_SLOW_RTT`
+/// (ms) say otherwise.
+const BRIDGE_FAST_RATE_MIB: u64 = 1024;
+const BRIDGE_FAST_RTT_MS: u64 = 5;
 const BRIDGE_SLOW_RATE_MIB: u64 = 50;
 const BRIDGE_SLOW_RTT_MS: u64 = 500;
 
-/// A writer on a fast transport (5 ms round trips, 1 GiB/s), a bridge on it and a slow
-/// one (500 ms round trips, 50 MiB/s, by default), and a node on the slow one alone: a writes 256
+/// A writer on a fast transport (5 ms round trips, 1 GiB/s, by default), a bridge on it
+/// and a slow one (500 ms round trips, 50 MiB/s), and a node on the slow one alone: a writes 256
 /// KiB values at 100 a second (25 MiB/s, a quarter of the fast link, half of the slow
 /// one), b passes them on to z. What z gets, as sync messages and as blobs (deltas),
 /// against what was written, and how late.
@@ -685,21 +688,23 @@ async fn bench_bridge() {
             .unwrap_or(default)
     };
     let writes = env("BENCH_BRIDGE_WRITES", BRIDGE_WRITES as u64) as usize;
+    let fast_rate = env("BENCH_BRIDGE_FAST_RATE", BRIDGE_FAST_RATE_MIB);
+    let fast_rtt = env("BENCH_BRIDGE_FAST_RTT", BRIDGE_FAST_RTT_MS);
     let slow_rate = env("BENCH_BRIDGE_SLOW_RATE", BRIDGE_SLOW_RATE_MIB);
     let slow_rtt = env("BENCH_BRIDGE_SLOW_RTT", BRIDGE_SLOW_RTT_MS);
     let sim = Sim::with_identity(71);
-    sim.net.set_default_link(LinkParams {
-        delay: (Duration::from_micros(2_000), Duration::from_micros(3_000)),
-        rate: Some(1 << 30),
-        ..LinkParams::default()
-    });
-    // Half the round trip each way, give or take a twentieth.
-    let half = Duration::from_millis(slow_rtt / 2);
-    sim.net_for("sim2").set_default_link(LinkParams {
-        delay: (half - half / 20, half + half / 20),
-        rate: Some(slow_rate << 20),
-        ..LinkParams::default()
-    });
+    // Half the round trip each way, give or take a fifth.
+    let link = |rate_mib: u64, rtt_ms: u64| {
+        let half = Duration::from_micros(rtt_ms * 500);
+        LinkParams {
+            delay: (half - half / 5, half + half / 5),
+            rate: Some(rate_mib << 20),
+            ..LinkParams::default()
+        }
+    };
+    sim.net.set_default_link(link(fast_rate, fast_rtt));
+    sim.net_for("sim2")
+        .set_default_link(link(slow_rate, slow_rtt));
     let timing = |config: &mut crate::node::NodeConfig| {
         config.timing = Timing::new(KEEPALIVE, SYNC_REPLY_TIMEOUT, DELIVERY_LIMIT);
         config.neighbours_k = 12;
@@ -763,7 +768,7 @@ async fn bench_bridge() {
             .map_or("beyond the last bucket".to_owned(), |ms| format!("{ms} ms"))
     };
     println!(
-        "\nfast writer, bridge, slow node ({writes} values of {} KiB, {} a second; slow link {slow_rate} MiB/s, {slow_rtt} ms round trips)\n  \
+        "\nfast writer, bridge, slow node ({writes} values of {} KiB, {} a second; fast link {fast_rate} MiB/s, {fast_rtt} ms round trips; slow link {slow_rate} MiB/s, {slow_rtt} ms round trips)\n  \
          written: {:.1} MiB in {:.1} s; z converged {} ms after the last write\n  \
          b sent (to a and z): SYNC {} messages, {:.1} MiB; BLOB {} messages, {:.1} MiB\n  \
          z received: SYNC {} messages, {:.1} MiB; BLOB {} messages, {:.1} MiB: {:.2} times what was written\n  \
-- 
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