fix(codecache): report the real runtime-stubs cache size by rkennke · Pull Request #681 · DataDog/java-profiler

rkennke · 2026-07-22T13:35:36Z

What

Fixes CODECACHE_RUNTIME_STUBS_SIZE_BYTES to report the JIT runtime-stubs code cache, instead of duplicating the native-libraries size.

Why

The counter was set to native_libs.memoryUsage() — the same expression as CODECACHE_NATIVE_SIZE_BYTES on the line above — a copy-paste present since it was introduced (d0b0d1e44 "add counters for codecaches"). So it never reflected the runtime stubs; it just double-reported the native-libs total.

The runtime stubs are a separate cache: JitCodeCache::_runtime_stubs (name "[stubs]"), populated via JitCodeCache::DynamicCodeGenerated() → add() as the JVM emits VM stubs. (There is also an unrelated, unused Libraries::_runtime_stubs member — same name, different thing; the live one is in JitCodeCache.)

How

Add JitCodeCache::runtimeStubsMemoryUsage(), which reads _runtime_stubs.memoryUsage() under _stubs_lock.lockShared(). That cache is mutated concurrently by the DynamicCodeGenerated JVMTI callback (add()/expand() under _stubs_lock), so the read must hold the shared lock — mirroring findRuntimeStub().
Set CODECACHE_RUNTIME_STUBS_SIZE_BYTES from it in Profiler::dump().

hotspot/jitCodeCache.* is compiled for all VM targets; on non-HotSpot VMs the callback never fires, so the cache is empty and the counter reports its (small, constant) empty-cache baseline rather than the wrong native-libs figure.

Notes

Scope: this PR fixes which cache the counter reflects (runtime stubs vs. the copy-pasted native-libs value). With fix(codecache): make memoryUsage() accurate and live #677 now merged, CodeCache::memoryUsage() is accurate, so this counter reports the real runtime-stubs footprint.
Rebased on latest main (which includes the merged fix(codecache): make memoryUsage() accurate and live #677 accuracy fix), so no duplicate accuracy work is needed here.
No unit test: _runtime_stubs is private and populated only by the JVMTI callback, so it can't be driven from gtest. Exercised by the JVM integration tests in CI (dump populates the counter).

Testing

:ddprof-lib:gtestDebug green — 349 tests, 0 failures.

🤖 Generated with Claude Code

Copilot

Pull request overview

Fixes the CODECACHE_RUNTIME_STUBS_SIZE_BYTES counter to report the HotSpot JIT runtime-stubs cache size (instead of incorrectly duplicating the native-libraries code cache size), improving the accuracy of codecache-related diagnostics emitted by Profiler::dump().

Changes:

Wire CODECACHE_RUNTIME_STUBS_SIZE_BYTES to JitCodeCache::_runtime_stubs.memoryUsage() instead of native_libs.memoryUsage().
Add JitCodeCache::runtimeStubsMemoryUsage() that reads under the shared stubs lock to avoid races with concurrent JVMTI DynamicCodeGenerated() updates.
Include the necessary hotspot/jitCodeCache.h dependency from profiler.cpp.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
ddprof-lib/src/main/cpp/profiler.cpp	Sets `CODECACHE_RUNTIME_STUBS_SIZE_BYTES` from `JitCodeCache::runtimeStubsMemoryUsage()` instead of duplicating native libs size.
ddprof-lib/src/main/cpp/hotspot/jitCodeCache.h	Declares `runtimeStubsMemoryUsage()` with concurrency rationale.
ddprof-lib/src/main/cpp/hotspot/jitCodeCache.cpp	Implements `runtimeStubsMemoryUsage()` using `_stubs_lock.lockShared()` around `_runtime_stubs.memoryUsage()`.

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dd-octo-sts · 2026-07-22T13:56:27Z

CI Test Results

Run:#30073266182 | Commit:ad97309 | Duration: 14m 54s (longest job)

✅ All 32 test jobs passed

Status Overview

JDK	glibc-aarch64/debug	glibc-amd64/debug	musl-aarch64/debug	musl-amd64/debug
8	-	✅	-	-
8-ibm	-	✅	-	-
8-j9	✅	✅	-	-
8-librca	-	-	✅	✅
8-orcl	-	✅	-	-
11	-	✅	-	-
11-j9	✅	✅	-	-
11-librca	-	-	✅	✅
17	✅	✅	-	-
17-graal	✅	✅	-	-
17-j9	✅	✅	-	-
17-librca	-	-	✅	✅
21	✅	✅	-	-
21-graal	✅	✅	-	-
21-librca	-	-	✅	✅
25	✅	✅	-	-
25-graal	✅	✅	-	-
25-librca	-	-	✅	✅

Legend: ✅ passed | ❌ failed | ⚪ skipped | 🚫 cancelled

Summary: Total: 32 | Passed: 32 | Failed: 0

Updated: 2026-07-24 07:05:38 UTC

dd-octo-sts · 2026-07-22T14:13:24Z

Benchmark Results (commit `8c422a3`)

Pipeline: https://gitlab.ddbuild.io/DataDog/apm-reliability/benchmarking-platform/-/pipelines/126245147 Commit: 8c422a30432280584f389c4aa4427007f1385c03

✅ Within expected boundaries

No significant runtime deltas (all within run-to-run noise) and no internal-counter outliers.

Runtime details (per benchmark × JDK)

Benchmark	JDK	Latest	Dev	Δ (dev vs latest)	Issues L/D
akka-uct	21	✅ 10332 ms (21 iters)	✅ 10170 ms (21 iters)	≈ -1.6% (±11.1%)	— / —
akka-uct	25	✅ 8849 ms (24 iters)	✅ 8865 ms (24 iters)	≈ +0.2% (±11%)	— / —
finagle-chirper	21	✅ 5998 ms (33 iters)	✅ 5981 ms (33 iters)	≈ -0.3% (±25.2%)	⚠️ W:3 / ⚠️ W:3
fj-kmeans	21	✅ 2752 ms (68 iters)	✅ 2686 ms (70 iters)	≈ -2.4% (±2.7%)	— / —
fj-kmeans	25	✅ 2818 ms (66 iters)	✅ 2749 ms (69 iters)	≈ -2.4% (±2.6%)	— / —
future-genetic	21	✅ 2091 ms (88 iters)	✅ 2073 ms (90 iters)	≈ -0.9% (±2.6%)	— / —
future-genetic	25	✅ 2064 ms (90 iters)	✅ 2048 ms (91 iters)	≈ -0.8% (±2.6%)	— / —
naive-bayes	21	✅ 1257 ms (136 iters)	✅ 1265 ms (135 iters)	≈ +0.6% (±32.4%)	— / —
naive-bayes	25	✅ 983 ms (173 iters)	✅ 1014 ms (169 iters)	≈ +3.2% (±32%)	— / —
reactors	21	✅ 16352 ms (15 iters)	✅ 16136 ms (15 iters)	≈ -1.3% (±6.9%)	— / —
reactors	25	✅ 18512 ms (15 iters)	✅ 18450 ms (15 iters)	≈ -0.3% (±5.8%)	— / —

Internal counter details (ddprof)

ddprof internal counters, latest / dev (✅ = 0, · = unavailable):

Benchmark	JDK	Dropped rec	Dropped jvmti	Dropped trace	Skipped WC	AGCT fail	Unwind fail
akka-uct	21	✅ / ✅	✅ / ✅	1 / 2	1941 / 2072	✅ / ✅	✅ / ✅
akka-uct	25	✅ / ✅	✅ / ✅	✅ / 1	2346 / 2182	✅ / ✅	✅ / ✅
finagle-chirper	21	✅ / ✅	✅ / ✅	2 / 5	8580 / 8611	✅ / ✅	✅ / ✅
fj-kmeans	21	✅ / ✅	✅ / ✅	6 / 2	1262 / 1255	✅ / ✅	✅ / ✅
fj-kmeans	25	✅ / ✅	✅ / ✅	✅ / 2	1290 / 1308	✅ / ✅	✅ / ✅
future-genetic	21	✅ / ✅	✅ / ✅	✅ / ✅	✅ / ✅	✅ / ✅	✅ / ✅
future-genetic	25	✅ / ✅	✅ / ✅	1 / ✅	2870 / 2900	✅ / ✅	✅ / ✅
naive-bayes	21	✅ / ✅	✅ / ✅	3 / 3	3516 / 3537	✅ / ✅	✅ / ✅
naive-bayes	25	✅ / ✅	✅ / ✅	4 / 5	3421 / 3449	✅ / ✅	✅ / ✅
reactors	21	✅ / ✅	✅ / ✅	1 / 1	1627 / 1622	✅ / ✅	✅ / ✅
reactors	25	✅ / ✅	✅ / ✅	✅ / 1	1936 / 1909	✅ / ✅	✅ / ✅

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dd-octo-sts · 2026-07-22T14:27:08Z

Reliability & Chaos Results

✅ All reliability & chaos checks passed Pipeline: https://gitlab.ddbuild.io/DataDog/java-profiler/-/pipelines/126561737

rkennke · 2026-07-22T14:29:44Z

Correct that the magnitude is still approximate here — but that's by design of the split, not something to fix in this PR:

This PR fixes which cache the counter reflects: CODECACHE_RUNTIME_STUBS_SIZE_BYTES was a copy-paste of native_libs.memoryUsage() and never pointed at the runtime-stubs cache at all. After this, it reads JitCodeCache::_runtime_stubs (under its lock).
The accuracy of memoryUsage() — the exact _capacity*sizeof(CodeBlob*) + _count*sizeof(NativeFunc) undercount you flagged — is fixed in fix(codecache): make memoryUsage() accurate and live #677, which rewrites CodeCache::memoryUsage() to count the real CodeBlob array + variable-length NativeFunc name allocations + DWARF table. That applies to everymemoryUsage()-based counter, including this one and CODECACHE_NATIVE_SIZE_BYTES.

So #681 + #677 together give an accurate runtime-stubs figure; keeping the accuracy fix in one place (#677) avoids duplicating/rebasing the same memoryUsage() change across PRs. Until #677 lands, this counter carries the same naive approximation as the sibling native_libs counter — no worse, and now at least attributed to the correct cache. I've made that explicit in the PR description.

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

rkennke · 2026-07-22T15:15:18Z

Reworded the comment to "approximate heap usage" (from "live heap footprint") and noted that CodeCache::memoryUsage() is a capacity/count estimate today, made exact by #677. Same underlying point as the codex P2 above — this PR fixes which cache the counter reflects; #677 fixes the magnitude.

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

dd-octo-sts · 2026-07-22T15:45:58Z

Benchmark Results (commit `2886d41`)

Pipeline: https://gitlab.ddbuild.io/DataDog/apm-reliability/benchmarking-platform/-/pipelines/126276523 Commit: 2886d411b833bf8b8e12ed533ac8b62139ea982b

⚠️ Significant outliers

🔴 fj-kmeans (JDK 21): runtime +3.2% (2695→2780 ms)

Runtime details (per benchmark × JDK)

Benchmark	JDK	Latest	Dev	Δ (dev vs latest)	Issues L/D
akka-uct	21	✅ 10301 ms (21 iters)	✅ 10255 ms (21 iters)	≈ -0.4% (±11.7%)	— / —
akka-uct	25	✅ 8866 ms (24 iters)	✅ 8851 ms (24 iters)	≈ -0.2% (±10.2%)	— / —
finagle-chirper	21	✅ 6010 ms (33 iters)	✅ 5981 ms (33 iters)	≈ -0.5% (±25%)	⚠️ W:3 / ⚠️ W:3
finagle-chirper	25	✅ 5450 ms (36 iters)	✅ 5463 ms (36 iters)	≈ +0.2% (±24.9%)	⚠️ W:3 / ⚠️ W:3
fj-kmeans	21	✅ 2695 ms (70 iters)	✅ 2780 ms (67 iters)	🔴 +3.2%	— / —
fj-kmeans	25	✅ 2827 ms (66 iters)	✅ 2809 ms (66 iters)	≈ -0.6% (±2.6%)	— / —
future-genetic	25	✅ 2115 ms (88 iters)	✅ 2071 ms (90 iters)	≈ -2.1% (±2.6%)	— / —
naive-bayes	21	✅ 1322 ms (130 iters)	✅ 1262 ms (136 iters)	≈ -4.5% (±31.6%)	— / —
naive-bayes	25	✅ 1020 ms (168 iters)	✅ 999 ms (172 iters)	≈ -2.1% (±31.3%)	— / —
reactors	21	✅ 16568 ms (15 iters)	✅ 17173 ms (15 iters)	≈ +3.7% (±7.6%)	— / —
reactors	25	✅ 18482 ms (15 iters)	✅ 18271 ms (15 iters)	≈ -1.1% (±5.5%)	— / —

Internal counter details (ddprof)

ddprof internal counters, latest / dev (✅ = 0, · = unavailable):

Benchmark	JDK	Dropped rec	Dropped jvmti	Dropped trace	Skipped WC	AGCT fail	Unwind fail
akka-uct	21	✅ / ✅	✅ / ✅	2 / 1	1960 / 2005	✅ / ✅	✅ / ✅
akka-uct	25	✅ / ✅	✅ / ✅	3 / 3	2153 / 2334	✅ / ✅	✅ / ✅
finagle-chirper	21	✅ / ✅	✅ / ✅	2 / 1	8594 / 8571	✅ / ✅	✅ / ✅
finagle-chirper	25	✅ / ✅	✅ / ✅	1 / 1	8022 / 8344	✅ / ✅	✅ / ✅
fj-kmeans	21	✅ / ✅	✅ / ✅	✅ / 1	1273 / 1304	✅ / ✅	✅ / ✅
fj-kmeans	25	✅ / ✅	✅ / ✅	3 / ✅	1278 / 1268	✅ / ✅	✅ / ✅
future-genetic	25	✅ / ✅	✅ / ✅	✅ / 3	2864 / 2825	✅ / ✅	✅ / ✅
naive-bayes	21	✅ / ✅	✅ / ✅	4 / 2	3542 / 3487	✅ / ✅	✅ / ✅
naive-bayes	25	✅ / ✅	✅ / ✅	2 / ✅	3473 / 3500	✅ / ✅	✅ / ✅
reactors	21	✅ / ✅	✅ / ✅	✅ / ✅	1574 / 1749	✅ / ✅	✅ / ✅
reactors	25	✅ / ✅	✅ / ✅	✅ / 2	1873 / 1701	✅ / ✅	✅ / ✅

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

Copilot

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

dd-octo-sts · 2026-07-23T11:30:59Z

Benchmark Results (commit `0742b45`)

Pipeline: https://gitlab.ddbuild.io/DataDog/apm-reliability/benchmarking-platform/-/pipelines/126484118 Commit: 0742b4542e099bf424fb63ecfc5a92414070c48c

⚠️ Significant outliers

🔴 fj-kmeans (JDK 21): runtime +2.7% (2745→2819 ms)

Runtime details (per benchmark × JDK)

Benchmark	JDK	Latest	Dev	Δ (dev vs latest)	Issues L/D
akka-uct	21	✅ 10297 ms (21 iters)	✅ 10304 ms (21 iters)	≈ +0.1% (±11.3%)	— / —
akka-uct	25	✅ 8896 ms (24 iters)	✅ 8921 ms (24 iters)	≈ +0.3% (±9.7%)	— / —
finagle-chirper	21	✅ 5944 ms (33 iters)	✅ 6013 ms (33 iters)	≈ +1.2% (±25.9%)	⚠️ W:3 / ⚠️ W:4
finagle-chirper	25	✅ 5472 ms (36 iters)	✅ 5453 ms (36 iters)	≈ -0.3% (±24%)	⚠️ W:3 / ⚠️ W:3
fj-kmeans	21	✅ 2745 ms (68 iters)	✅ 2819 ms (66 iters)	🔴 +2.7%	— / —
fj-kmeans	25	✅ 2835 ms (66 iters)	✅ 2833 ms (66 iters)	≈ -0.1% (±2.6%)	— / —
future-genetic	21	✅ 2087 ms (89 iters)	✅ 2041 ms (90 iters)	≈ -2.2% (±2.6%)	— / —
future-genetic	25	✅ 2096 ms (88 iters)	✅ 2071 ms (89 iters)	≈ -1.2% (±2.6%)	— / —
naive-bayes	21	✅ 1243 ms (137 iters)	✅ 1281 ms (134 iters)	≈ +3.1% (±33.1%)	— / —
naive-bayes	25	✅ 1000 ms (171 iters)	✅ 1007 ms (170 iters)	≈ +0.7% (±31.4%)	— / —
reactors	21	✅ 16383 ms (15 iters)	✅ 15786 ms (15 iters)	≈ -3.6% (±7.5%)	— / —

Internal counter details (ddprof)

ddprof internal counters, latest / dev (✅ = 0, · = unavailable):

Benchmark	JDK	Dropped rec	Dropped jvmti	Dropped trace	Skipped WC	AGCT fail	Unwind fail
akka-uct	21	✅ / ✅	✅ / ✅	3 / 5	2019 / 2035	✅ / ✅	✅ / ✅
akka-uct	25	✅ / ✅	✅ / ✅	✅ / ✅	2224 / 2122	✅ / ✅	✅ / ✅
finagle-chirper	21	✅ / ✅	✅ / ✅	2 / 3	8454 / 8884	✅ / ✅	✅ / ✅
finagle-chirper	25	✅ / ✅	✅ / ✅	2 / ✅	8262 / 8260	✅ / ✅	✅ / ✅
fj-kmeans	21	✅ / ✅	✅ / ✅	1 / 1	1253 / 1246	✅ / ✅	✅ / ✅
fj-kmeans	25	✅ / ✅	✅ / ✅	✅ / ✅	1279 / 1283	✅ / ✅	✅ / ✅
future-genetic	21	✅ / ✅	✅ / ✅	4 / 3	3028 / 2878	✅ / ✅	✅ / ✅
future-genetic	25	✅ / ✅	✅ / ✅	✅ / 2	2859 / 2838	✅ / ✅	✅ / ✅
naive-bayes	21	✅ / ✅	✅ / ✅	1 / 4	3497 / 3520	✅ / ✅	✅ / ✅
naive-bayes	25	✅ / ✅	✅ / ✅	3 / 2	3489 / 3438	✅ / ✅	✅ / ✅
reactors	21	✅ / ✅	✅ / ✅	2 / 1	1642 / 1682	✅ / ✅	✅ / ✅

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dd-octo-sts · 2026-07-23T14:35:54Z

Benchmark Results (commit `b80dfc4`)

Pipeline: https://gitlab.ddbuild.io/DataDog/apm-reliability/benchmarking-platform/-/pipelines/126538514 Commit: b80dfc4a71f3df75be8d6fd44609a5a1b97a4850

✅ Within expected boundaries

No significant runtime deltas (all within run-to-run noise) and no internal-counter outliers.

Runtime details (per benchmark × JDK)

Benchmark	JDK	Latest	Dev	Δ (dev vs latest)	Issues L/D
akka-uct	21	✅ 10257 ms (21 iters)	✅ 10384 ms (21 iters)	≈ +1.2% (±11.1%)	— / —
akka-uct	25	✅ 8825 ms (24 iters)	✅ 8765 ms (24 iters)	≈ -0.7% (±9.8%)	— / —
finagle-chirper	21	✅ 6033 ms (33 iters)	✅ 6005 ms (33 iters)	≈ -0.5% (±25.4%)	⚠️ W:3 / ⚠️ W:3
finagle-chirper	25	✅ 5470 ms (36 iters)	✅ 5436 ms (36 iters)	≈ -0.6% (±24.2%)	⚠️ W:3 / ⚠️ W:4
fj-kmeans	21	✅ 2756 ms (68 iters)	✅ 2752 ms (68 iters)	≈ -0.1% (±2.8%)	— / —
fj-kmeans	25	✅ 2808 ms (66 iters)	✅ 2792 ms (67 iters)	≈ -0.6% (±2.6%)	— / —
future-genetic	21	✅ 2083 ms (89 iters)	✅ 2134 ms (88 iters)	≈ +2.4% (±2.7%)	— / —
future-genetic	25	✅ 2057 ms (91 iters)	✅ 2078 ms (89 iters)	≈ +1% (±2.6%)	— / —
naive-bayes	21	✅ 1273 ms (134 iters)	✅ 1253 ms (136 iters)	≈ -1.6% (±32.3%)	— / —
naive-bayes	25	✅ 1015 ms (168 iters)	✅ 1014 ms (169 iters)	≈ -0.1% (±31.8%)	— / —
reactors	21	✅ 16117 ms (15 iters)	✅ 15653 ms (16 iters)	≈ -2.9% (±7.8%)	— / —
reactors	25	✅ 18362 ms (15 iters)	✅ 18219 ms (15 iters)	≈ -0.8% (±4.4%)	— / —

Internal counter details (ddprof)

ddprof internal counters, latest / dev (✅ = 0, · = unavailable):

Benchmark	JDK	Dropped rec	Dropped jvmti	Dropped trace	Skipped WC	AGCT fail	Unwind fail
akka-uct	21	✅ / ✅	✅ / ✅	2 / 3	1982 / 1981	✅ / ✅	✅ / ✅
akka-uct	25	✅ / ✅	✅ / ✅	3 / 2	2353 / 2386	✅ / ✅	✅ / ✅
finagle-chirper	21	✅ / ✅	✅ / ✅	5 / 2	8205 / 8643	✅ / ✅	✅ / ✅
finagle-chirper	25	✅ / ✅	✅ / ✅	1 / 2	8380 / 8111	✅ / ✅	✅ / ✅
fj-kmeans	21	✅ / ✅	✅ / ✅	1 / 1	1253 / 1260	✅ / ✅	✅ / ✅
fj-kmeans	25	✅ / ✅	✅ / ✅	5 / ✅	1272 / 1279	✅ / ✅	✅ / ✅
future-genetic	21	✅ / ✅	✅ / ✅	1 / 3	3030 / 3007	✅ / ✅	✅ / ✅
future-genetic	25	✅ / ✅	✅ / ✅	1 / 4	2841 / 2834	✅ / ✅	✅ / ✅
naive-bayes	21	✅ / ✅	✅ / ✅	4 / 5	3510 / 3505	✅ / ✅	✅ / ✅
naive-bayes	25	✅ / ✅	✅ / ✅	2 / 3	3466 / 3500	✅ / ✅	✅ / ✅
reactors	21	✅ / ✅	✅ / ✅	✅ / 1	1570 / 1584	✅ / ✅	✅ / ✅
reactors	25	✅ / ✅	✅ / ✅	✅ / ✅	1936 / 1868	✅ / ✅	✅ / ✅

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dd-octo-sts · 2026-07-23T15:36:57Z

Benchmark Results (commit `f6ee1ce`)

Pipeline: https://gitlab.ddbuild.io/DataDog/apm-reliability/benchmarking-platform/-/pipelines/126561763 Commit: f6ee1ced5c7cb4921d8699e56402b87541a76cca

⚠️ Significant outliers

🔴 future-genetic (JDK 21): runtime +4.4% (2071→2162 ms)

Runtime details (per benchmark × JDK)

Benchmark	JDK	Latest	Dev	Δ (dev vs latest)	Issues L/D
akka-uct	21	✅ 10224 ms (21 iters)	✅ 10278 ms (21 iters)	≈ +0.5% (±12.1%)	— / —
akka-uct	25	✅ 8834 ms (24 iters)	✅ 8870 ms (24 iters)	≈ +0.4% (±10%)	— / —
finagle-chirper	21	✅ 6008 ms (33 iters)	✅ 6014 ms (33 iters)	≈ +0.1% (±24.7%)	⚠️ W:3 / ⚠️ W:3
fj-kmeans	21	✅ 2771 ms (68 iters)	✅ 2774 ms (68 iters)	≈ +0.1% (±2.8%)	— / —
fj-kmeans	25	✅ 2803 ms (66 iters)	✅ 2837 ms (66 iters)	≈ +1.2% (±2.6%)	— / —
future-genetic	21	✅ 2071 ms (89 iters)	✅ 2162 ms (86 iters)	🔴 +4.4%	— / —
naive-bayes	21	✅ 1241 ms (139 iters)	✅ 1297 ms (133 iters)	≈ +4.5% (±33%)	— / —
naive-bayes	25	✅ 970 ms (176 iters)	✅ 997 ms (171 iters)	≈ +2.8% (±32%)	— / —
reactors	21	✅ 15680 ms (15 iters)	✅ 16453 ms (15 iters)	≈ +4.9% (±7.7%)	— / —
reactors	25	✅ 18106 ms (15 iters)	✅ 18265 ms (15 iters)	≈ +0.9% (±5.8%)	— / —

Internal counter details (ddprof)

ddprof internal counters, latest / dev (✅ = 0, · = unavailable):

Benchmark	JDK	Dropped rec	Dropped jvmti	Dropped trace	Skipped WC	AGCT fail	Unwind fail
akka-uct	21	✅ / ✅	✅ / ✅	✅ / ✅	✅ / ✅	✅ / ✅	✅ / ✅
akka-uct	25	✅ / ✅	✅ / ✅	3 / 2	2339 / 2394	✅ / ✅	✅ / ✅
finagle-chirper	21	✅ / ✅	✅ / ✅	2 / 5	8689 / 8640	✅ / ✅	✅ / ✅
fj-kmeans	21	✅ / ✅	✅ / ✅	3 / ✅	1288 / 1264	✅ / ✅	✅ / ✅
fj-kmeans	25	✅ / ✅	✅ / ✅	4 / 1	1254 / 1290	✅ / ✅	✅ / ✅
future-genetic	21	✅ / ✅	✅ / ✅	1 / ✅	3092 / 2993	✅ / ✅	✅ / ✅
naive-bayes	21	✅ / ✅	✅ / ✅	8 / 1	3576 / 3480	✅ / ✅	✅ / ✅
naive-bayes	25	✅ / ✅	✅ / ✅	6 / 2	3504 / 3472	✅ / ✅	✅ / ✅
reactors	21	✅ / ✅	✅ / ✅	1 / 1	1552 / 1675	✅ / ✅	✅ / ✅
reactors	25	✅ / ✅	✅ / ✅	4 / 2	1814 / 1744	✅ / ✅	✅ / ✅

CODECACHE_RUNTIME_STUBS_SIZE_BYTES was set to native_libs.memoryUsage() — the same value as CODECACHE_NATIVE_SIZE_BYTES — a copy-paste since the counter was introduced (d0b0d1e). It never reflected the runtime-stubs cache. The runtime stubs live in JitCodeCache::_runtime_stubs (populated by DynamicCodeGenerated as the JVM emits stubs), a different cache from the native libraries. Add JitCodeCache::runtimeStubsMemoryUsage(), which reads that cache's size under its shared _stubs_lock (the cache is mutated concurrently by the JVMTI callback), and set the counter from it. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

…ootprint" CodeCache::memoryUsage() is a capacity/count-based estimate on main, so "live heap footprint" overstated it. Reword to "approximate heap usage" and note #677 makes memoryUsage() exact. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

…age is exact With #677 merged, CodeCache::memoryUsage() is accurate on main, so the runtime-stubs accessor comment describing it as an approximation (pending #677) is no longer true. Describe current behavior. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

The runtime-stubs memory counter called the HotSpot-specific JitCodeCache::runtimeStubsMemoryUsage() directly from shared profiler.cpp, with no VM guard. On J9/Zing that reports a fixed near-zero baseline with nothing in the code marking the value as meaningless there. Route it through the same JVMSupport -> HotspotSupport abstraction the sibling isJitCode() accessor uses: JVMSupport::runtimeStubsMemoryUsage() dispatches to HotspotSupport (-> JitCodeCache) on HotSpot and returns 0 elsewhere. profiler.cpp no longer references JitCodeCache directly. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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dd-octo-sts · 2026-07-24T07:14:55Z

Benchmark Results (commit `df34493`)

Pipeline: https://gitlab.ddbuild.io/DataDog/apm-reliability/benchmarking-platform/-/pipelines/126711785 Commit: df34493a9499f571fdee30235b6bc1a9c831a31a

⚠️ Significant outliers

🟢 future-genetic (JDK 25): runtime -2.7% (2090→2033 ms)

Runtime details (per benchmark × JDK)

Benchmark	JDK	Latest	Dev	Δ (dev vs latest)	Issues L/D
akka-uct	21	✅ 10393 ms (21 iters)	✅ 10316 ms (21 iters)	≈ -0.7% (±11.5%)	— / —
akka-uct	25	✅ 8979 ms (24 iters)	✅ 8961 ms (24 iters)	≈ -0.2% (±10.5%)	— / —
finagle-chirper	21	✅ 5990 ms (33 iters)	✅ 5949 ms (33 iters)	≈ -0.7% (±25.3%)	⚠️ W:3 / ⚠️ W:3
finagle-chirper	25	✅ 5461 ms (36 iters)	✅ 5455 ms (36 iters)	≈ -0.1% (±24.2%)	⚠️ W:3 / ⚠️ W:3
fj-kmeans	21	✅ 2695 ms (70 iters)	✅ 2724 ms (68 iters)	≈ +1.1% (±2.7%)	— / —
fj-kmeans	25	✅ 2810 ms (67 iters)	✅ 2807 ms (67 iters)	≈ -0.1% (±2.6%)	— / —
future-genetic	21	✅ 2052 ms (90 iters)	✅ 2072 ms (89 iters)	≈ +1% (±2.6%)	— / —
future-genetic	25	✅ 2090 ms (89 iters)	✅ 2033 ms (91 iters)	🟢 -2.7%	— / —
naive-bayes	21	✅ 1304 ms (131 iters)	✅ 1260 ms (136 iters)	≈ -3.4% (±32.1%)	— / —
naive-bayes	25	✅ 1015 ms (168 iters)	✅ 1018 ms (168 iters)	≈ +0.3% (±32.1%)	— / —
reactors	21	✅ 16064 ms (15 iters)	✅ 15890 ms (15 iters)	≈ -1.1% (±7.4%)	— / —
reactors	25	✅ 18184 ms (15 iters)	✅ 18546 ms (15 iters)	≈ +2% (±5.3%)	— / —

Internal counter details (ddprof)

ddprof internal counters, latest / dev (✅ = 0, · = unavailable):

Benchmark	JDK	Dropped rec	Dropped jvmti	Dropped trace	Skipped WC	AGCT fail	Unwind fail
akka-uct	21	✅ / ✅	✅ / ✅	4 / 1	2023 / 2013	✅ / ✅	✅ / ✅
akka-uct	25	✅ / ✅	✅ / ✅	1 / 6	2391 / 2139	✅ / ✅	✅ / ✅
finagle-chirper	21	✅ / ✅	✅ / ✅	3 / 7	8405 / 8109	✅ / ✅	✅ / ✅
finagle-chirper	25	✅ / ✅	✅ / ✅	1 / 1	8605 / 8190	✅ / ✅	✅ / ✅
fj-kmeans	21	✅ / ✅	✅ / ✅	5 / ✅	1295 / 1250	✅ / ✅	✅ / ✅
fj-kmeans	25	✅ / ✅	✅ / ✅	2 / 3	1317 / 1312	✅ / ✅	✅ / ✅
future-genetic	21	✅ / ✅	✅ / ✅	2 / 3	2958 / 2969	✅ / ✅	✅ / ✅
future-genetic	25	✅ / ✅	✅ / ✅	✅ / 3	2910 / 2893	✅ / ✅	✅ / ✅
naive-bayes	21	✅ / ✅	✅ / ✅	3 / 2	3483 / 3497	✅ / ✅	✅ / ✅
naive-bayes	25	✅ / ✅	✅ / ✅	3 / 4	3422 / 3502	✅ / ✅	✅ / ✅
reactors	21	✅ / ✅	✅ / ✅	2 / ✅	1640 / 1556	✅ / ✅	✅ / ✅
reactors	25	✅ / ✅	✅ / ✅	✅ / ✅	1778 / 1933	✅ / ✅	✅ / ✅

jbachorik

Thanks! LGTM!

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feat(nativemem): categorized native-memory accounting — first cut #669
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Comment threadddprof-lib/src/main/cpp/profiler.cpp

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Bump java-profiler (ddprof) to 1.48.0 DataDog/dd-trace-java#12076
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Benchmark Results (commit 8c422a3)

✅ Within expected boundaries

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Benchmark Results (commit 2886d41)

⚠️ Significant outliers

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Benchmark Results (commit 0742b45)

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Benchmark Results (commit `2886d41`)

Benchmark Results (commit `0742b45`)

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Benchmark Results (commit `f6ee1ce`)

Benchmark Results (commit `df34493`)