[PROF-15076] Fix GC profiling being disabled on Ruby 3.2.10/3.2.11 by ivoanjo · Pull Request #5894 · DataDog/dd-trace-rb

ivoanjo · 2026-06-12T16:35:43Z

What does this PR do?

This PR introduces a new RubyVersion helper and moves profiling code to use it.

This fixes a bug with our GC profiling logic testing using strings directly, and 3.2.10/3.2.11 are unfortunately < "3.2.3", e.g.:

if ...
    (RUBY_VERSION.start_with?("3.2.") && RUBY_VERSION < "3.2.3")
  logger.warn(
    "Current Ruby version (#{RUBY_VERSION}) has a VM bug where enabling GC profiling would cause " \
    "crashes (https://bugs.ruby-lang.org/issues/18464). GC profiling has been disabled."
  )

Motivation:

Fix feature being mistakenly broken on latest Ruby patch versions.

Change log entry

Yes. Fix GC profiling being disabled on Ruby 3.2.10/3.2.11

Additional Notes:

I admit I knew about this footgun, but there hadn't been .10 and above releases in a while and I kinda disliked the verboseness of doing the check using Gem::Version or the like.

With the addition of the helper, we can do it correctly and cleanly.

I've also changed every other use in profiling of RUBY_VERSION.

I'm preparing a follow-up PR to change this in more places in dd-trace-rb, but wanted to get this out as a smaller fix first.

Finally, I've split the change into step-by-step commits, and I recommend reviewing commit-by-commit.

How to test the change?

This change has test coverage.

…out boilerplate

**What does this PR do?** This PR introduces a new `RubyVersion` helper and moves profiling code to use it. This fixes a bug with our GC profiling logic testing using strings directly, and `3.2.10`/`3.2.11` are unfortunately `< "3.2.3"`, e.g.: ```ruby if ... (RUBY_VERSION.start_with?("3.2.") && RUBY_VERSION < "3.2.3") logger.warn( "Current Ruby version (#{RUBY_VERSION}) has a VM bug where enabling GC profiling would cause " \ "crashes (https://bugs.ruby-lang.org/issues/18464). GC profiling has been disabled." ) ``` **Motivation:** Fix feature being mistakenly broken on latest Ruby patch versions. **Additional Notes:** I admit I knew about this footgun, but there hadn't been .10 and above releases in a while and I kinda disliked the verboseness of doing the check using `Gem::Version` or the like. With the addition of the helper, we can do it correctly and cleanly. I've also changed every other use in profiling of `RUBY_VERSION`. **How to test the change?** This change has test coverage.

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datadog-datadog-prod-us1 · 2026-06-12T16:44:16Z

Tests

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 36.84%
• Overall Coverage: 89.87% (-0.01%)

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

🔗 Commit SHA: 8f3d166 | Docs | Datadog PR Page | Give us feedback!}

eregon

Good cleanup but I'm not very fond of ~> it's quite verbose (needs an extra digit when most cases want to check e.g. >= A.B) and error-prone (e.g. when forgetting to add the extra digit) and probably quite slow.
I'd prefer something like if RubyVersion >= 3.4/if RubyVersion >= [3, 4]/if RubyVersion >= "3.4"

eregon · 2026-06-15T11:58:58Z

Thinking out loud, for cases like 3.1.0 - 3.1.2 we could have:

if RubyVersion.between?("3.1.0", "3.1.2") # There is Comparable#between? which we might be able to reuse
if RubyVersion.in?("3.1.0".."3.1.2")

Though just this is fine too:

if RubyVersion >= "3.1.0" && RubyVersion <= "3.1.2"

((or (ab)use the fact such checks are typically single-digits and ("3.1.0".."3.1.2").include?(RUBY_VERSION)))

ivoanjo · 2026-06-15T12:36:37Z

Thinking out loud, for cases like 3.1.0 - 3.1.2 we could have

I agree; yet, when I looked at it, I think we have less than 5? 10? of those, so having the extra helper didn't seem worth the extra code.

Co-authored-by: Benoit Daloze <[email protected]>

pr-commenter · 2026-06-15T13:18:55Z

Benchmarks

Benchmark execution time: 2026-06-15 16:42:52

Comparing candidate commit b7af24e in PR branch ivoanjo/prof-15076-gc-profiling-disabled-ruby-3.2.11 with baseline commit 202d652 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 48 metrics, 1 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 ----------------------------------'

…confusing

Oops

**What does this PR do?** In #5894 we added a new `RubyVersion` helper to have a short and always-correct way of guarding code that needs to behave differently across Ruby versions. In that PR I deliberately did not touch code outside of profiling, and this is the follow-up that adds the helper to the rest of dd-trace-rb. **Motivation:** Standardize on `RubyVersion` as the common way of testing `RUBY_VERSION`. **Additional Notes:** N/A **How to test the change?** This change is covered by the existing tests.

ivoanjo added 4 commits June 12, 2026 11:28

Add RubyVersion helper to make it easier to do accurate checks with…

929df19

…out boilerplate

Add failing test for bug with GC Profiling being incorrectly disabled

d592004

Move profiling specs to use new RubyVersion helper

632246f

ivoanjo requested review from a team as code owners June 12, 2026 16:35

ivoanjo requested a review from eregon June 12, 2026 16:35

dd-octo-sts Bot added core Involves Datadog core libraries profiling Involves Datadog profiling labels Jun 12, 2026

chatgpt-codex-connector Bot reviewed Jun 12, 2026

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Comment thread lib/datadog/profiling/ext/dir_monkey_patches.rb Outdated

ivoanjo mentioned this pull request Jun 15, 2026

[PROF-15076] Adopt RubyVersion helper outside of profiling #5901

Merged

eregon reviewed Jun 15, 2026

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ivoanjo added 3 commits June 15, 2026 13:18

Avoid recreating Gem::Version every time

15851f5

Tweak version check for readibility

3f9530b

Improve comments around usage of rb_obj_info

51cff9f

ivoanjo added 2 commits June 15, 2026 13:42

Stub CURRENT_RUBY_VERSION as the RubyVersion helper caches it on-load

4bf9b9e

Clarify comment around use of extend RubyVersion

9e76743

eregon reviewed Jun 15, 2026

View reviewed changes

Comment thread lib/datadog/ruby_version.rb Outdated

Update lib/datadog/ruby_version.rb

6b35805

Co-authored-by: Benoit Daloze <[email protected]>

ivoanjo added 2 commits June 15, 2026 16:08

Avoid using ~> (twiddle-wakka) for version comparsions, as it can be …

b7af24e

…confusing

Fix incorrect change to spec

8f3d166

Oops

Strech approved these changes Jun 15, 2026

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marcotc approved these changes Jun 15, 2026

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eregon approved these changes Jun 16, 2026

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ivoanjo merged commit 9f17636 into master Jun 16, 2026
589 checks passed

ivoanjo deleted the ivoanjo/prof-15076-gc-profiling-disabled-ruby-3.2.11 branch June 16, 2026 08:12

dd-octo-sts Bot added this to the 2.36.0 milestone Jun 16, 2026

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[PROF-15076] Fix GC profiling being disabled on Ruby 3.2.10/3.2.11#5894

[PROF-15076] Fix GC profiling being disabled on Ruby 3.2.10/3.2.11#5894
ivoanjo merged 12 commits into
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ivoanjo/prof-15076-gc-profiling-disabled-ruby-3.2.11

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