RPC Pressure Evidence

This file records the current synthetic RPC responsiveness guard for aria2-rust-pro.

Scope

Current guard coverage is synthetic but no longer limited to a single tellStatus loop:

in-process dispatcher
BT-like magnet workload
repeated aria2.tellStatus
sampled aria2.getFiles
repeated aria2.tellActive
repeated aria2.tellGlobalStat
Criterion rpc_mixed_pressure and bt_visibility_pressure anchors

This is not a public-swarm benchmark. It is a deterministic regression guard for scheduler/RPC responsiveness while the runtime is still approximation-heavy.

Guard Tests

rpc_bt_pressure_guard_keeps_status_active_and_global_stat_responsive
rpc_bt_mixed_pressure_guard_covers_churned_status_files_and_global_views

Basic guard shape:

64 BT-like magnet tasks
4 pressure rounds
256 total tellStatus calls
4 tellActive calls
4 tellGlobalStat calls
runtime tick updates injected during the loop to keep non-zero BT-like state

Mixed guard shape:

96 BT-like magnet tasks
6 pressure rounds
576 total tellStatus calls
72 sampled getFiles calls
6 tellActive calls
6 tellGlobalStat calls
per-download runtime tick churn before every status probe

Current Thresholds

These thresholds are deliberately broad. They are there to catch obvious regressions, not to certify final performance:

cumulative tellStatus time across the run: <= 2000ms
cumulative tellActive time across the run: <= 500ms
cumulative tellGlobalStat time across the run: <= 500ms
cumulative mixed guard time across the run: <= 4000ms

Current Criterion Anchors

Current focused Criterion runs on this host:

Benchmark	Mean	95% CI
`rpc_mixed_pressure/mixed_rpc/96`	`92.383 us`	`90.867 .. 93.895 us`
`rpc_mixed_pressure/mixed_rpc/192`	`175.169 us`	`160.464 .. 192.884 us`
`bt_visibility_pressure/bt_visibility/32`	`2.3293 ms`	`1.0756 .. 4.0986 ms`
`bt_visibility_pressure/bt_visibility/64`	`2.1302 ms`	`2.0707 .. 2.2057 ms`

Interpretation:

the deterministic integration tests now cover mixed BT/RPC status, file, and global-stat surfaces under runtime churn
the Criterion anchors give a current non-HTTP performance regression guard
the thresholds remain intentionally broad so host-local noise does not turn a synthetic guard into a flaky gate

Next Steps

Further work should extend this guard with:

explicit scheduler tick pressure
resource counters suitable for later perf reporting
a documented comparison against the C++ reference once comparable benchmark suites exist

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