fix(compression): align zstd behavior across targets by rochdev · Pull Request #2400 · DataDog/libdatadog

rochdev · 2026-08-24T15:03:29Z

What does this PR do?

Addresses follow-up review feedback from #2386:

restores the pre-feat(compression): use zrip for wasm targets #2386 Miri FFI explanation in the profile test helper;
documents the WASM and native zstd compression-level contracts;
maps level 0 to level 3 on every target;
clamps WASM zrip levels to -7..=4 while preserving native zstd's broader range;
reports the effective compression level from trace compression;
isolates target-specific trace encoder construction and shares the write/finish path; and
tests native passthrough and WASM clamping at both boundaries.

Motivation

The zrip WASM backend supports a narrower compression-level range than native zstd and previously assigned a different meaning to level 0. Out-of-range levels also disabled trace compression or failed profile compression under WASM. The target branches duplicated the common encoder flow.

This follows up on these review threads:

Additional Notes

Native targets continue to accept the broader range reported by zstd::compression_level_range(). WASM clamps requested levels to zrip's supported range, so level 22 becomes 4; level 0 becomes 3 on every target.

The full trace-utils integration binary was not validated locally because Docker could not pull the private GHCR test-agent image. All 348 trace-utils library tests passed. Strict trace-utils clippy also reports an existing collapsible_match warning in unchanged tracer_payload.rs; clippy passes with that lint allowed.

This PR was generated by Codex.

How to test the change?

cargo test -p libdd-profiling
cargo test -p libdd-trace-utils --features compression --lib
env CARGO_TARGET_WASM32_UNKNOWN_UNKNOWN_RUNNER=wasm-bindgen-test-runner cargo test -p libdd-wasm-tests --target wasm32-unknown-unknown
cargo +stable clippy -p libdd-profiling --all-targets -- -D warnings
cargo +stable clippy -p libdd-wasm-tests --target wasm32-unknown-unknown --all-targets -- -D warnings
cargo +stable clippy -p libdd-trace-utils --all-targets --features compression -- -D warnings -A clippy::collapsible_match
cargo +nightly-2026-07-26 fmt --all -- --check
cargo test -p libdd-profiling --doc
cargo test -p libdd-trace-utils --features compression --doc

datadog-datadog-prod-us1 · 2026-08-24T15:15:28Z

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 76.63% (-0.00%)

_{This comment will be updated automatically if new data arrives.

🔗 Commit SHA: e5dc6ef | Docs | View more details | Give us feedback!}

pr-commenter · 2026-08-24T15:38:36Z

Benchmarks

Comparison

Benchmark execution time: 2026-08-24 18:46:29

Comparing candidate commit e5dc6ef in PR branch rochdev/address-compression-review with baseline commit 394c7e2 in branch main.

Found 1 performance improvements and 1 performance regressions! Performance is the same for 104 metrics, 10 unstable metrics.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

🟩 = significantly better candidate vs. baseline
🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

scenario:datadog_sample_span/resource_pattern_rule_not_matching/wall_time

🟥 execution_time [+18.729ns; +18.795ns] or [+11.692%; +11.733%]

scenario:glob_matcher/unicode_exact_match/wall_time

🟩 execution_time [-5.699ns; -5.650ns] or [-7.152%; -7.091%]

Candidate

Omitted due to size.

Baseline

Omitted due to size.

dd-octo-sts · 2026-08-24T15:44:56Z

Artifact Size Benchmark Report

aarch64-alpine-linux-musl

Artifact	Baseline	Commit	Change
/aarch64-alpine-linux-musl/lib/libdatadog_profiling.a	89.52 MB	89.52 MB	+0% (+8 B) 👌
/aarch64-alpine-linux-musl/lib/libdatadog_profiling.so	8.26 MB	8.26 MB	0% (0 B) 👌

aarch64-unknown-linux-gnu

Artifact	Baseline	Commit	Change
/aarch64-unknown-linux-gnu/lib/libdatadog_profiling.so	11.06 MB	11.06 MB	0% (0 B) 👌
/aarch64-unknown-linux-gnu/lib/libdatadog_profiling.a	100.70 MB	100.70 MB	+0% (+8 B) 👌

libdatadog-x64-windows

Artifact	Baseline	Commit	Change
/libdatadog-x64-windows/debug/dynamic/datadog_profiling_ffi.dll	26.64 MB	26.64 MB	+.01% (+4.00 KB) 🔍
/libdatadog-x64-windows/debug/dynamic/datadog_profiling_ffi.lib	94.96 KB	94.96 KB	0% (0 B) 👌
/libdatadog-x64-windows/debug/dynamic/datadog_profiling_ffi.pdb	180.73 MB	180.75 MB	+0% (+16.00 KB) 👌
/libdatadog-x64-windows/debug/static/datadog_profiling_ffi.lib	772.85 MB	773.55 MB	+.08% (+708.91 KB) 🔍
/libdatadog-x64-windows/release/dynamic/datadog_profiling_ffi.dll	8.73 MB	8.73 MB	0% (0 B) 👌
/libdatadog-x64-windows/release/dynamic/datadog_profiling_ffi.lib	94.96 KB	94.96 KB	0% (0 B) 👌
/libdatadog-x64-windows/release/dynamic/datadog_profiling_ffi.pdb	25.65 MB	25.65 MB	0% (0 B) 👌
/libdatadog-x64-windows/release/static/datadog_profiling_ffi.lib	51.09 MB	51.09 MB	0% (0 B) 👌

libdatadog-x86-windows

Artifact	Baseline	Commit	Change
/libdatadog-x86-windows/debug/dynamic/datadog_profiling_ffi.dll	23.22 MB	23.22 MB	+0% (+512 B) 👌
/libdatadog-x86-windows/debug/dynamic/datadog_profiling_ffi.lib	96.45 KB	96.45 KB	0% (0 B) 👌
/libdatadog-x86-windows/debug/dynamic/datadog_profiling_ffi.pdb	185.66 MB	185.66 MB	-0% (-8.00 KB) 👌
/libdatadog-x86-windows/debug/static/datadog_profiling_ffi.lib	759.09 MB	759.28 MB	+.02% (+198.03 KB) 🔍
/libdatadog-x86-windows/release/dynamic/datadog_profiling_ffi.dll	6.74 MB	6.74 MB	0% (0 B) 👌
/libdatadog-x86-windows/release/dynamic/datadog_profiling_ffi.lib	96.45 KB	96.45 KB	0% (0 B) 👌
/libdatadog-x86-windows/release/dynamic/datadog_profiling_ffi.pdb	27.59 MB	27.59 MB	0% (0 B) 👌
/libdatadog-x86-windows/release/static/datadog_profiling_ffi.lib	48.62 MB	48.62 MB	-0% (-2 B) 👌

x86_64-alpine-linux-musl

Artifact	Baseline	Commit	Change
/x86_64-alpine-linux-musl/lib/libdatadog_profiling.a	79.78 MB	79.78 MB	0% (0 B) 👌
/x86_64-alpine-linux-musl/lib/libdatadog_profiling.so	9.16 MB	9.16 MB	0% (0 B) 👌

x86_64-unknown-linux-gnu

Artifact	Baseline	Commit	Change
/x86_64-unknown-linux-gnu/lib/libdatadog_profiling.a	95.42 MB	95.42 MB	0% (0 B) 👌
/x86_64-unknown-linux-gnu/lib/libdatadog_profiling.so	11.17 MB	11.17 MB	0% (0 B) 👌

rochdev · 2026-08-25T11:59:49Z

/merge

gh-worker-devflow-routing-ef8351 · 2026-08-25T11:59:53Z

View all feedbacks in Devflow UI.

2026-08-25 11:59:53 UTC ℹ️ Start processing command /merge

2026-08-25 11:59:59 UTC ℹ️ MergeQueue: pull request added to the queue

The expected merge time in main is approximately 60m (p90).

2026-08-25 12:45:50 UTC ℹ️ MergeQueue: This merge request was merged

fix(compression): align zstd behavior across targets

0b43c24

github-actions Bot added the mini-agent label Aug 24, 2026

test(profiling): skip native zstd under miri

0ccc548

fix(compression): clamp zrip compression levels

2fa7bbb

rochdev marked this pull request as ready for review August 24, 2026 18:08

rochdev requested review from a team as code owners August 24, 2026 18:08

docs(profiling): restore miri explanation

e5dc6ef

bengl reviewed Aug 24, 2026

View reviewed changes

Comment thread libdd-profiling/src/pprof/test_utils.rs Outdated

bengl approved these changes Aug 24, 2026

View reviewed changes

gh-worker-dd-devflow-36fce6 Bot added mergequeue-status: queued mergequeue-status: in_progress and removed mergequeue-status: queued labels Aug 25, 2026

gh-worker-dd-mergequeue-cf854d Bot merged commit a25619e into main Aug 25, 2026
108 of 111 checks passed

gh-worker-dd-devflow-36fce6 Bot removed the mergequeue-status: in_progress label Aug 25, 2026

gh-worker-dd-mergequeue-cf854d Bot deleted the rochdev/address-compression-review branch August 25, 2026 12:45

gh-worker-dd-devflow-36fce6 Bot added the mergequeue-status: done label Aug 25, 2026

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fix(compression): align zstd behavior across targets - #2400

fix(compression): align zstd behavior across targets#2400
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scenario:glob_matcher/unicode_exact_match/wall_time

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