Bugfix: use p75 for min block test as per eval doc

doc/measuring-minimum-block-time.md

@@ -13,10 +13,10 @@ The missions perform the binary search to find the minimum sustainable block tim
 
 A candidate close time `T` is considered a **pass** if and only if, **on every node in the network**, the stellar-core `ledger.age.closed-histogram` metric satisfies **both** of the following:
 
-* **P50** (median) is in the range `[0.80·T, 1.20·T)` ms  *(temporary; see note below)*
+* **P75** is in the range `[0.80·T, 1.20·T)` ms  *(temporary; see note below)*
 * **P99** is `≤ 2·T` ms
 
-> **FIXME (P50 tolerance):** the intended P50 band is `[0.95·T, 1.05·T)` (±5%), but stellar-core currently has performance regressions that prevent the stricter band from being achievable under load. The tolerance has been temporarily widened to ±20% so the test can exercise the rest of the pipeline; tighten it back to ±5% (or narrower) once those regressions are fixed.
+> **FIXME (P75 tolerance):** the intended P75 band is `[0.95·T, 1.05·T)` (±5%), but stellar-core currently has performance regressions that prevent the stricter band from being achievable under load. The tolerance has been temporarily widened to ±20% so the test can exercise the rest of the pipeline; tighten it back to ±5% (or narrower) once those regressions are fixed.
 
 If any node violates any of these bounds, `T` is considered a **fail** and the binary search raises its lower bound. The same is true if the load run itself errors (e.g., stellar-core's internal `loadgen-run-failed` counter increments, nodes fall out of sync, or peers report inconsistent ledger hashes) — in that case the mission treats the iteration as a fail and the search continues upward.
 

doc/missions.md

@@ -153,7 +153,7 @@ Stress test a network of simulated Tier1 topology with a mix of classic and soro
 
 ## MissionMinBlockTimeClassic
 
-Find the minimum ledger target close time a simulated Tier1 network can sustain at a fixed TPS while meeting a per-node `ledger.age.closed` latency SLA (P50 within ±20% of target, P99 ≤ 2×), driving classic-payment load. See [Running minimum block time test](measuring-minimum-block-time.md) for details.
+Find the minimum ledger target close time a simulated Tier1 network can sustain at a fixed TPS while meeting a per-node `ledger.age.closed` latency SLA (P75 within ±20% of target, P99 ≤ 2×), driving classic-payment load. See [Running minimum block time test](measuring-minimum-block-time.md) for details.
 
 ## MissionMinBlockTimeMixed
 

src/FSLibrary/MinBlockTimeTest.fs

@@ -28,13 +28,13 @@ let private timeoutsFor (targetMs: int) : int = max 500 (targetMs / 5)
 
 let private readLedgerAgePercentiles (peer: Peer) : float * float =
     let h = peer.GetMetrics().LedgerAgeClosedHistogram
-    float h.Median, float h.``99``
+    float h.``75``, float h.``99``
 
 // Returns true iff every peer's ledger.age.closed-histogram satisfies:
-//   P50 in [0.80*T, 1.20*T)
+//   P75 in [0.80*T, 1.20*T)
 //   P99 <= 2*T
 //
-// FIXME: the P50 tolerance is temporarily widened to +/-20% because
+// FIXME: the P75 tolerance is temporarily widened to +/-20% because
 // stellar-core currently has perf regressions that prevent the intended
 // +/-5% band from being achievable. Tighten this back to 0.95/1.05 (or
 // lower) once those regressions are fixed.
@@ -48,14 +48,14 @@ let private checkLedgerAgeSLA (formation: StellarFormation) (coreSets: CoreSet l
     formation.NetworkCfg.EachPeerInSets
         (List.toArray coreSets)
         (fun peer ->
-            let p50, p99 = readLedgerAgePercentiles peer
-            let peerOk = p50 >= tLo && p50 < tHi && p99 <= p99Max
+            let p75, p99 = readLedgerAgePercentiles peer
+            let peerOk = p75 >= tLo && p75 < tHi && p99 <= p99Max
 
             LogInfo
-                "peer=%s T=%dms p50=%.0f p99=%.0f -> %s"
+                "peer=%s T=%dms p75=%.0f p99=%.0f -> %s"
                 peer.ShortName.StringName
                 targetMs
-                p50
+                p75
                 p99
                 (if peerOk then "PASS" else "FAIL")
 

src/FSLibrary/MissionMinBlockTimeClassic.fs

@@ -6,9 +6,9 @@ module MissionMinBlockTimeClassic
 
 // Mirror of MissionMaxTPSClassic for the minimum-block-time search: fixes the
 // TPS at --tx-rate and binary-searches for the smallest ledger target close
-// time (in [--min-block-time-ms, 6000] ms) that still keeps ledger.age.closed
-// within the currently enforced SLA checks (P50 within a widened band around
-// T, and P99 <= 2T; no P99.9 bound is currently enforced here).
+// time (in [--min-block-time-ms, --max-block-time-ms] ms) that still keeps
+// ledger.age.closed-histogram within the currently enforced SLA checks (P75
+// within a widened band around T, and P99 <= 2T).
 
 open MinBlockTimeTest
 open StellarMissionContext

src/FSLibrary/MissionMinBlockTimeMixed.fs

@@ -6,7 +6,7 @@ module MissionMinBlockTimeMixed
 
 // Mirror of MissionMaxTPSMixed for the minimum-block-time search: mixed
 // classic + Soroban workload at a fixed TPS, binary-searches for the smallest
-// ledger target close time that still keeps ledger.age.closed within SLA.
+// ledger target close time that still keeps ledger.age.closed-histogram within SLA.
 
 open MinBlockTimeTest
 open PubnetData