chore(transport/fc): add debug_assert to catch underflow #3209
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Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## main #3209 +/- ##
==========================================
- Coverage 93.49% 93.46% -0.04%
==========================================
Files 125 125
Lines 36674 36677 +3
Branches 36674 36677 +3
==========================================
- Hits 34290 34280 -10
- Misses 1540 1553 +13
Partials 844 844
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Pull request overview
This PR adds a debug assertion to the flow control code to detect unexpected underflow conditions during max_active value updates. The assertion helps diagnose issue #3208 by catching cases where max_active decreases when it shouldn't, providing detailed debug information when the assertion fails.
Key Changes
- Added a
debug_assert!in the flow control update logic to verify thatmax_activenever decreases relative to its previous value - Included comprehensive debug context (self state, timing, RTT, max_window, subject) in the assertion message for troubleshooting
larseggert
approved these changes
Dec 5, 2025
Contributor
Client/server transfer resultsPerformance differences relative to d070393. Transfer of 33554432 bytes over loopback, min. 100 runs. All unit-less numbers are in milliseconds.
Table above only shows statistically significant changes. See all results below. All resultsTransfer of 33554432 bytes over loopback, min. 100 runs. All unit-less numbers are in milliseconds.
Download data for |
Contributor
Failed Interop TestsQUIC Interop Runner, client vs. server, differences relative to d070393.
All resultsSucceeded Interop TestsQUIC Interop Runner, client vs. server neqo-latest as client
neqo-latest as server
Unsupported Interop TestsQUIC Interop Runner, client vs. server neqo-latest as client
neqo-latest as server
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Contributor
Benchmark resultsSignificant performance differences relative to d070393. 1-conn/10_000-parallel-1b-resp/mtu-1504 (aka. RPS)/client: 💔 Performance has regressed by +2.1036%. time: [285.14 ms 287.22 ms 289.31 ms]
thrpt: [34.564 Kelem/s 34.817 Kelem/s 35.070 Kelem/s]
change:
time: [+1.0892% +2.1036% +3.1037] (p = 0.00 < 0.05)
thrpt: [-3.0103% -2.0603% -1.0775]
Performance has regressed.
Found 2 outliers among 100 measurements (2.00%)
2 (2.00%) high mildAll results1-conn/1-100mb-resp/mtu-1504 (aka. Download)/client: No change in performance detected. time: [206.73 ms 207.02 ms 207.32 ms]
thrpt: [482.34 MiB/s 483.04 MiB/s 483.72 MiB/s]
change:
time: [-0.2941% +0.0503% +0.3376] (p = 0.77 > 0.05)
thrpt: [-0.3364% -0.0502% +0.2950]
No change in performance detected.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mild1-conn/10_000-parallel-1b-resp/mtu-1504 (aka. RPS)/client: 💔 Performance has regressed by +2.1036%. time: [285.14 ms 287.22 ms 289.31 ms]
thrpt: [34.564 Kelem/s 34.817 Kelem/s 35.070 Kelem/s]
change:
time: [+1.0892% +2.1036% +3.1037] (p = 0.00 < 0.05)
thrpt: [-3.0103% -2.0603% -1.0775]
Performance has regressed.
Found 2 outliers among 100 measurements (2.00%)
2 (2.00%) high mild1-conn/1-1b-resp/mtu-1504 (aka. HPS)/client: No change in performance detected. time: [38.486 ms 38.642 ms 38.824 ms]
thrpt: [25.757 B/s 25.878 B/s 25.984 B/s]
change:
time: [-1.0187% -0.3679% +0.2949] (p = 0.28 > 0.05)
thrpt: [-0.2940% +0.3692% +1.0291]
No change in performance detected.
Found 7 outliers among 100 measurements (7.00%)
2 (2.00%) high mild
5 (5.00%) high severe1-conn/1-100mb-req/mtu-1504 (aka. Upload)/client: Change within noise threshold. time: [212.24 ms 212.59 ms 212.97 ms]
thrpt: [469.56 MiB/s 470.40 MiB/s 471.16 MiB/s]
change:
time: [+0.7692% +1.1783% +1.5064] (p = 0.00 < 0.05)
thrpt: [-1.4840% -1.1646% -0.7633]
Change within noise threshold.
Found 2 outliers among 100 measurements (2.00%)
2 (2.00%) high severedecode 4096 bytes, mask ff: No change in performance detected. time: [11.331 µs 11.374 µs 11.422 µs]
change: [-0.7854% -0.2529% +0.2478] (p = 0.36 > 0.05)
No change in performance detected.
Found 16 outliers among 100 measurements (16.00%)
3 (3.00%) low severe
2 (2.00%) low mild
1 (1.00%) high mild
10 (10.00%) high severedecode 1048576 bytes, mask ff: No change in performance detected. time: [2.9955 ms 3.0051 ms 3.0163 ms]
change: [-0.3333% +0.1563% +0.5975] (p = 0.53 > 0.05)
No change in performance detected.
Found 10 outliers among 100 measurements (10.00%)
10 (10.00%) high severedecode 4096 bytes, mask 7f: No change in performance detected. time: [19.580 µs 19.638 µs 19.702 µs]
change: [-0.4748% -0.0716% +0.3323] (p = 0.74 > 0.05)
No change in performance detected.
Found 14 outliers among 100 measurements (14.00%)
3 (3.00%) low mild
1 (1.00%) high mild
10 (10.00%) high severedecode 1048576 bytes, mask 7f: No change in performance detected. time: [5.0319 ms 5.0498 ms 5.0730 ms]
change: [-0.3586% +0.1003% +0.6433] (p = 0.71 > 0.05)
No change in performance detected.
Found 14 outliers among 100 measurements (14.00%)
14 (14.00%) high severedecode 4096 bytes, mask 3f: No change in performance detected. time: [6.2001 µs 6.2209 µs 6.2492 µs]
change: [-0.5434% +0.2025% +0.9851] (p = 0.64 > 0.05)
No change in performance detected.
Found 15 outliers among 100 measurements (15.00%)
5 (5.00%) low mild
4 (4.00%) high mild
6 (6.00%) high severedecode 1048576 bytes, mask 3f: No change in performance detected. time: [1.7582 ms 1.7639 ms 1.7715 ms]
change: [-0.2923% +0.1819% +0.6895] (p = 0.53 > 0.05)
No change in performance detected.
Found 6 outliers among 100 measurements (6.00%)
2 (2.00%) high mild
4 (4.00%) high severe1-streams/each-1000-bytes/wallclock-time: No change in performance detected. time: [583.23 µs 585.50 µs 588.02 µs]
change: [-0.7770% -0.2457% +0.2777] (p = 0.38 > 0.05)
No change in performance detected.
Found 9 outliers among 100 measurements (9.00%)
9 (9.00%) high severe1-streams/each-1000-bytes/simulated-time: No change in performance detected. time: [118.79 ms 119.02 ms 119.25 ms]
thrpt: [8.1891 KiB/s 8.2047 KiB/s 8.2208 KiB/s]
change:
time: [-0.3676% -0.1029% +0.1713] (p = 0.46 > 0.05)
thrpt: [-0.1710% +0.1030% +0.3690]
No change in performance detected.1000-streams/each-1-bytes/wallclock-time: No change in performance detected. time: [12.324 ms 12.364 ms 12.403 ms]
change: [-0.6860% -0.2386% +0.1597] (p = 0.28 > 0.05)
No change in performance detected.1000-streams/each-1-bytes/simulated-time: No change in performance detected. time: [2.3254 s 2.3293 s 2.3333 s]
thrpt: [428.58 B/s 429.31 B/s 430.03 B/s]
change:
time: [-0.3250% -0.1207% +0.0844] (p = 0.25 > 0.05)
thrpt: [-0.0844% +0.1209% +0.3261]
No change in performance detected.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mild1000-streams/each-1000-bytes/wallclock-time: Change within noise threshold. time: [49.651 ms 49.763 ms 49.877 ms]
change: [-0.7194% -0.4011% -0.0709] (p = 0.02 < 0.05)
Change within noise threshold.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mild1000-streams/each-1000-bytes/simulated-time: No change in performance detected. time: [16.267 s 16.516 s 16.768 s]
thrpt: [58.240 KiB/s 59.127 KiB/s 60.035 KiB/s]
change:
time: [-1.8918% +0.2367% +2.5106] (p = 0.83 > 0.05)
thrpt: [-2.4491% -0.2361% +1.9283]
No change in performance detected.coalesce_acked_from_zero 1+1 entries: No change in performance detected. time: [89.095 ns 89.375 ns 89.664 ns]
change: [-0.4092% +0.0384% +0.4978] (p = 0.86 > 0.05)
No change in performance detected.
Found 10 outliers among 100 measurements (10.00%)
7 (7.00%) high mild
3 (3.00%) high severecoalesce_acked_from_zero 3+1 entries: No change in performance detected. time: [105.78 ns 106.07 ns 106.39 ns]
change: [-0.4078% -0.0084% +0.3758] (p = 0.97 > 0.05)
No change in performance detected.
Found 10 outliers among 100 measurements (10.00%)
10 (10.00%) high severecoalesce_acked_from_zero 10+1 entries: No change in performance detected. time: [105.44 ns 106.06 ns 106.93 ns]
change: [+0.1770% +1.2525% +2.8566] (p = 0.05 > 0.05)
No change in performance detected.
Found 13 outliers among 100 measurements (13.00%)
2 (2.00%) low severe
2 (2.00%) low mild
9 (9.00%) high severecoalesce_acked_from_zero 1000+1 entries: No change in performance detected. time: [91.230 ns 91.333 ns 91.455 ns]
change: [-0.7059% -0.1313% +0.4484] (p = 0.67 > 0.05)
No change in performance detected.
Found 16 outliers among 100 measurements (16.00%)
5 (5.00%) high mild
11 (11.00%) high severeRxStreamOrderer::inbound_frame(): No change in performance detected. time: [109.32 ms 109.52 ms 109.84 ms]
change: [-0.6058% -0.2860% +0.0205] (p = 0.07 > 0.05)
No change in performance detected.
Found 6 outliers among 100 measurements (6.00%)
2 (2.00%) low mild
1 (1.00%) high mild
3 (3.00%) high severesent::Packets::take_ranges: No change in performance detected. time: [4.3984 µs 4.4841 µs 4.5564 µs]
change: [-3.2373% -0.3348% +2.8364] (p = 0.83 > 0.05)
No change in performance detected.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mildtransfer/pacing-false/varying-seeds/wallclock-time/run: Change within noise threshold. time: [25.034 ms 25.070 ms 25.107 ms]
change: [-1.2690% -1.0488% -0.8379] (p = 0.00 < 0.05)
Change within noise threshold.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mildtransfer/pacing-false/varying-seeds/simulated-time/run: No change in performance detected. time: [25.153 s 25.188 s 25.223 s]
thrpt: [162.39 KiB/s 162.62 KiB/s 162.84 KiB/s]
change:
time: [-0.1276% +0.0627% +0.2657] (p = 0.53 > 0.05)
thrpt: [-0.2650% -0.0626% +0.1277]
No change in performance detected.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mildtransfer/pacing-true/varying-seeds/wallclock-time/run: Change within noise threshold. time: [25.474 ms 25.513 ms 25.556 ms]
change: [-0.6246% -0.3942% -0.1761] (p = 0.00 < 0.05)
Change within noise threshold.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high severetransfer/pacing-true/varying-seeds/simulated-time/run: Change within noise threshold. time: [24.886 s 24.924 s 24.961 s]
thrpt: [164.10 KiB/s 164.34 KiB/s 164.59 KiB/s]
change:
time: [+0.0271% +0.2288% +0.4403] (p = 0.03 < 0.05)
thrpt: [-0.4383% -0.2283% -0.0271]
Change within noise threshold.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mildtransfer/pacing-false/same-seed/wallclock-time/run: Change within noise threshold. time: [24.915 ms 24.982 ms 25.049 ms]
change: [-0.6906% -0.3720% -0.0602] (p = 0.02 < 0.05)
Change within noise threshold.transfer/pacing-false/same-seed/simulated-time/run: No change in performance detected. time: [25.234 s 25.234 s 25.234 s]
thrpt: [162.32 KiB/s 162.32 KiB/s 162.32 KiB/s]
change:
time: [+0.0000% +0.0000% +0.0000] (p = NaN > 0.05)
thrpt: [+0.0000% +0.0000% +0.0000]
No change in performance detected.transfer/pacing-true/same-seed/wallclock-time/run: Change within noise threshold. time: [25.706 ms 25.735 ms 25.778 ms]
change: [+0.6641% +0.9201% +1.1566] (p = 0.00 < 0.05)
Change within noise threshold.
Found 2 outliers among 100 measurements (2.00%)
1 (1.00%) high mild
1 (1.00%) high severetransfer/pacing-true/same-seed/simulated-time/run: No change in performance detected. time: [25.207 s 25.207 s 25.207 s]
thrpt: [162.50 KiB/s 162.50 KiB/s 162.50 KiB/s]
change:
time: [+0.0000% +0.0000% +0.0000] (p = NaN > 0.05)
thrpt: [+0.0000% +0.0000% +0.0000]
No change in performance detected.Download data for |
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If I only knew how to hit it, I wouldn't need the @larseggert would you mind merging manually? I don't have the permissions. |
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Needed for #3208.