On the `master` (v0.2.x) branch, we track the number of scoped dispatchers currently active, and use it to determine whether or not to check thread-local storage at all. This optimization was introduced in PR #1017. It turns out that this change prevents the incorrect behavior where a `None` dispatcher is cached in the thread local if a scoped dispatcher is used before the global default is set (issue #2587). Therefore, this commit backports the `SCOPED_COUNT` optimization (and *just* the `SCOPED_COUNT` change) from #1017 to the `v0.1.x` branch. Currently, this results in a substantial performance *regression*, especially in the "no dispatcher" case. This is because the `None` dispatcher gets cloned a lot now that it's no longer cached. A subsequent commit will resolve this by backporting more of the changes from #1017, but I wanted to make this in a separate commit to determine if it fixes the tests for #2587. ``` Running benches/dispatch_get_clone.rs (target/release/deps/dispatch_get_clone-d4d6ca1f9895e432) Dispatch::get_clone/none time: [23.525 ns 23.534 ns 23.543 ns] change: [+113.37% +113.59% +113.79%] (p = 0.00 < 0.05) Performance has regressed. Found 3 outliers among 100 measurements (3.00%) 2 (2.00%) low mild 1 (1.00%) high mild Dispatch::get_clone/scoped time: [11.071 ns 11.078 ns 11.084 ns] change: [-0.1603% -0.0360% +0.1300%] (p = 0.67 > 0.05) No change in performance detected. Found 8 outliers among 100 measurements (8.00%) 3 (3.00%) low severe 3 (3.00%) low mild 1 (1.00%) high mild 1 (1.00%) high severe Dispatch::get_clone/global time: [24.036 ns 24.055 ns 24.075 ns] change: [+118.73% +119.28% +119.84%] (p = 0.00 < 0.05) Performance has regressed. Found 3 outliers among 100 measurements (3.00%) 1 (1.00%) high mild 2 (2.00%) high severe Running benches/dispatch_get_ref.rs (target/release/deps/dispatch_get_ref-6ce05749a0b1bf87) Dispatch::get_ref/none time: [14.326 ns 14.365 ns 14.407 ns] change: [+265.93% +266.48% +267.13%] (p = 0.00 < 0.05) Performance has regressed. Found 9 outliers among 100 measurements (9.00%) 4 (4.00%) high mild 5 (5.00%) high severe Dispatch::get_ref/scoped time: [3.8639 ns 3.8681 ns 3.8725 ns] change: [+0.3381% +0.6460% +0.9565%] (p = 0.00 < 0.05) Change within noise threshold. Found 10 outliers among 100 measurements (10.00%) 2 (2.00%) low mild 3 (3.00%) high mild 5 (5.00%) high severe Dispatch::get_ref/global time: [14.378 ns 14.472 ns 14.586 ns] change: [+272.95% +274.50% +276.12%] (p = 0.00 < 0.05) Performance has regressed. Found 11 outliers among 100 measurements (11.00%) 2 (2.00%) low severe 4 (4.00%) low mild 2 (2.00%) high mild 3 (3.00%) high severe Running benches/empty_span.rs (target/release/deps/empty_span-745c777d77b8b7ca) empty_span/none time: [230.31 ps 230.47 ps 230.64 ps] change: [-0.9622% -0.8240% -0.6836%] (p = 0.00 < 0.05) Change within noise threshold. Found 5 outliers among 100 measurements (5.00%) 1 (1.00%) low mild 2 (2.00%) high mild 2 (2.00%) high severe empty_span/scoped time: [233.29 ps 233.90 ps 234.48 ps] change: [-0.0987% +0.1388% +0.3820%] (p = 0.28 > 0.05) No change in performance detected. Found 1 outliers among 100 measurements (1.00%) 1 (1.00%) high mild empty_span/global time: [234.41 ps 234.60 ps 234.78 ps] change: [-0.4066% -0.2249% -0.0607%] (p = 0.01 < 0.05) Change within noise threshold. Found 19 outliers among 100 measurements (19.00%) 5 (5.00%) low severe 13 (13.00%) low mild 1 (1.00%) high mild empty_span/baseline_struct time: [704.20 ps 704.52 ps 704.86 ps] change: [-0.2031% +0.0627% +0.2709%] (p = 0.64 > 0.05) No change in performance detected. Found 9 outliers among 100 measurements (9.00%) 3 (3.00%) low mild 3 (3.00%) high mild 3 (3.00%) high severe Running benches/enter_span.rs (target/release/deps/enter_span-7fc1c2a69c076475) enter_span/none time: [0.0000 ps 0.0000 ps 0.0000 ps] change: [-43.986% +9.0604% +110.03%] (p = 0.82 > 0.05) No change in performance detected. Found 12 outliers among 100 measurements (12.00%) 4 (4.00%) high mild 8 (8.00%) high severe enter_span/scoped time: [2.8087 ns 2.8171 ns 2.8263 ns] change: [-6.2503% -5.8437% -5.5244%] (p = 0.00 < 0.05) Performance has improved. Found 17 outliers among 100 measurements (17.00%) 10 (10.00%) low severe 4 (4.00%) low mild 2 (2.00%) high mild 1 (1.00%) high severe enter_span/global time: [2.7827 ns 2.7881 ns 2.7942 ns] change: [-7.0005% -6.6984% -6.3814%] (p = 0.00 < 0.05) Performance has improved. Found 1 outliers among 100 measurements (1.00%) 1 (1.00%) high mild Running benches/event.rs (target/release/deps/event-6742eef6ebe07aa4) event/none time: [233.17 ps 233.70 ps 234.26 ps] change: [+0.8021% +1.2066% +1.7762%] (p = 0.00 < 0.05) Change within noise threshold. Found 21 outliers among 100 measurements (21.00%) 9 (9.00%) low severe 8 (8.00%) high mild 4 (4.00%) high severe event/scoped time: [9.5149 ns 9.5274 ns 9.5408 ns] change: [+4.4596% +4.6910% +4.8995%] (p = 0.00 < 0.05) Performance has regressed. Found 3 outliers among 100 measurements (3.00%) 3 (3.00%) high mild event/scoped_recording time: [33.624 ns 34.086 ns 34.597 ns] change: [-7.7753% +1.4363% +11.588%] (p = 0.80 > 0.05) No change in performance detected. Found 28 outliers among 100 measurements (28.00%) 12 (12.00%) low mild 4 (4.00%) high mild 12 (12.00%) high severe event/global time: [22.544 ns 22.587 ns 22.631 ns] change: [+143.27% +143.94% +144.64%] (p = 0.00 < 0.05) Performance has regressed. Found 7 outliers among 100 measurements (7.00%) 6 (6.00%) low severe 1 (1.00%) low mild Running benches/shared.rs (target/release/deps/shared-9c2531bf46089869) running 0 tests test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s Running benches/span_fields.rs (target/release/deps/span_fields-96dfd0a8a577dec6) span_fields/none time: [3.2739 ns 3.2814 ns 3.2900 ns] change: [+0.6402% +0.8871% +1.1473%] (p = 0.00 < 0.05) Change within noise threshold. Found 10 outliers among 100 measurements (10.00%) 4 (4.00%) high mild 6 (6.00%) high severe span_fields/scoped time: [29.177 ns 29.237 ns 29.283 ns] change: [-4.7079% -4.4906% -4.2912%] (p = 0.00 < 0.05) Performance has improved. span_fields/scoped_recording time: [269.00 ns 269.32 ns 269.64 ns] change: [+4.7209% +4.8928% +5.0580%] (p = 0.00 < 0.05) Performance has regressed. Found 5 outliers among 100 measurements (5.00%) 5 (5.00%) high mild span_fields/global time: [39.700 ns 39.860 ns 40.081 ns] change: [+31.179% +31.920% +33.131%] (p = 0.00 < 0.05) Performance has regressed. Found 3 outliers among 100 measurements (3.00%) 1 (1.00%) high mild 2 (2.00%) high severe Running benches/span_no_fields.rs (target/release/deps/span_no_fields-f8c7d7a84f720442) span_no_fields/none time: [1.3904 ns 1.3914 ns 1.3927 ns] change: [-2.2161% -2.0729% -1.9314%] (p = 0.00 < 0.05) Performance has improved. Found 11 outliers among 100 measurements (11.00%) 1 (1.00%) low mild 5 (5.00%) high mild 5 (5.00%) high severe span_no_fields/scoped time: [18.811 ns 18.818 ns 18.826 ns] change: [+1.9002% +2.1274% +2.3444%] (p = 0.00 < 0.05) Performance has regressed. Found 7 outliers among 100 measurements (7.00%) 1 (1.00%) high mild 6 (6.00%) high severe span_no_fields/scoped_recording time: [32.819 ns 32.844 ns 32.872 ns] change: [-0.2256% -0.1680% -0.1081%] (p = 0.00 < 0.05) Change within noise threshold. Found 10 outliers among 100 measurements (10.00%) 5 (5.00%) high mild 5 (5.00%) high severe span_no_fields/global time: [36.148 ns 36.190 ns 36.229 ns] change: [+91.653% +91.930% +92.168%] (p = 0.00 < 0.05) Performance has regressed. Found 6 outliers among 100 measurements (6.00%) 4 (4.00%) low severe 1 (1.00%) low mild 1 (1.00%) high mild Running benches/span_repeated.rs (target/release/deps/span_repeated-03bfaaf4ecd13d36) span_repeated/none time: [730.43 ns 731.10 ns 731.79 ns] change: [+0.8904% +1.1179% +1.3512%] (p = 0.00 < 0.05) Change within noise threshold. Found 4 outliers among 100 measurements (4.00%) 3 (3.00%) high mild 1 (1.00%) high severe span_repeated/scoped time: [2.4945 µs 2.4980 µs 2.5017 µs] change: [+3.4807% +3.6733% +3.8473%] (p = 0.00 < 0.05) Performance has regressed. Found 3 outliers among 100 measurements (3.00%) 1 (1.00%) low mild 2 (2.00%) high mild span_repeated/scoped_recording time: [4.9626 µs 4.9712 µs 4.9786 µs] change: [-1.2378% -0.8863% -0.5529%] (p = 0.00 < 0.05) Change within noise threshold. Found 1 outliers among 100 measurements (1.00%) 1 (1.00%) high mild span_repeated/global time: [3.8247 µs 3.8270 µs 3.8291 µs] change: [+55.811% +55.944% +56.091%] (p = 0.00 < 0.05) Performance has regressed. Found 1 outliers among 100 measurements (1.00%) 1 (1.00%) high severe ```

Commits

Commits on May 11, 2023