Antalya 25.8 Backport of #116836 - jemalloc: lower lg_extent_max_active_fit to default 6, to reduce fragmentation

[mkmkme]

jemalloc: lower lg_extent_max_active_fit to default 6, to reduce fragmentation

Changelog category (leave one):

• Performance Improvement

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

jemalloc: lower lg_extent_max_active_fit to default 6, to reduce fragmentation (ClickHouse#116836 by @azat)

Documentation entry for user-facing changes

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CI/CD Options

Exclude tests:

• Fast test
• Integration Tests
• Stateless tests
• Stateful tests
• Unit tests
• Performance tests
• Aarch64 tests
• All with ASAN
• All with TSAN
• All with MSAN
• All with UBSAN
• All with Coverage
• All Regression
• Disable CI Cache

Regression jobs to run:

• Fast suites (mostly <1h)
• Aggregate Functions (2h)
• Alter (1.5h)
• Benchmark (30m)
• CAS (content-addressed storage; Antalya only)
• ClickHouse Keeper (1h)
• Iceberg (2h)
• LDAP (1h)
• OAuth (5m)
• Parquet (1.5h)
• RBAC (1.5h)
• SSL Server (1h)
• S3 (2h)
• S3 Export (2h)
• Swarms (30m)
• Tiered Storage (2h)

[github-actions]

Workflow [PR], commit [07a13a4]

[mkmkme]

@blau-ai

[blau-ai]

CI triage for #2523

Verdict: 0 of the failures are caused by this PR. This backport changes exactly one line — lg_extent_max_active_fit:8 → :6 in contrib/jemalloc-cmake/CMakeLists.txt (an allocator fragmentation-tuning constant). It cannot plausibly produce query-engine logical errors, parquet-format test diffs, or image-CVE findings. Every red check below is pre-existing / flaky / infra. No fix is required on this PR.

Summary: 7 red checks — 2 infra (Grype), 3 flaky/pre-existing engine failures, 1 pre-existing regression feature, 1 aggregate gate.

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1–2. Grype Scan (keeper: 4 high/critical, server-alpine: 1) — infra / pre-existing

CVE scans of the built Docker images. These flag vulnerabilities in base-image packages and appear on essentially every Altinity PR; they are independent of source changes and of a CMake allocator flag. Next step: safe to ignore for this PR; handled by the image/dependency-update track.

3. Stateless tests (amd_binary, ParallelReplicas, s3 storage, parallel) — flaky / pre-existing

One failure: 03608_export_merge_tree_part_filename_pattern. Reference diff is in the "Custom prefix pattern" sub-case — the export of the single-row 2021 partition didn't produce the expected file:

 ---- Test: Custom prefix pattern
-4	2021
 ---- Verify filename matches myprefix_2021_2_2_0.1.parquet
-1
+0

This is a test of the Antalya parquet part-export feature — unrelated to the allocator change. It passed in every other stateless shard on this same commit (debug/asan/ubsan all green), which is the signature of a flaky export/format test rather than a regression. Next step: re-run the job; if it reproduces it belongs to the parquet-export feature owners, not this PR.

4. Stress test (amd_debug) — pre-existing engine bug

Server aborted on a LOGICAL_ERROR during a JOIN, not anything allocator-related:

<Fatal> Logical error: 'Unexpected return type from concat. Expected Nullable(String). Got String.'
query: SELECT concat(`__table2`.`id`, '_1') AS `id`, ... ALL LEFT JOIN ... USING (`id`) ORDER BY val
  DB::ExpressionActions::execute  (src/Interpreters/ExpressionActions.cpp:809)

A nullability/type-inference mismatch for concat over a LEFT JOIN key — a pre-existing analyzer/expression bug in 25.8, exercised by the stress fuzzer. Next step: track separately as an engine bug; not a blocker for this backport.

5. Stress test (amd_ubsan) — flaky / pre-existing (different crash)

Crashed with a different fatal error than the debug run:

<Fatal> Logical error: 'ReadBuffer is canceled. Can't read from it.'

Two different stress jobs dying with two unrelated logical errors is the signature of a generally-unstable stress suite on this branch, not a deterministic effect of one PR. A jemalloc fragmentation-ratio change would surface as allocator/OOM symptoms, not these high-level logical errors. Next step: re-run; pre-existing stress instability.

6. RegressionTestsRelease / Parquet / parquet (Regression x86 parquet) — pre-existing

1 of 39 features failed in the Parquet regression suite. Again a parquet-reader/format area, orthogonal to an allocator flag. Next step: compare against the latest antalya-25.8 base run; this feature failure is not introduced here.

7. PR — aggregate gate

Rolls up the above; goes green once the real checks are addressed/re-run. No independent error.

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Bottom line: the diff is a safe, self-contained allocator tuning backport of upstream ClickHouse#116836 (reverting the Q35 :8 experiment back to jemalloc's default :6 to reduce fragmentation). I'd re-run the two stress jobs and the ParallelReplicas stateless shard to clear the flakes; the Grype and parquet-regression reds are pre-existing and tracked elsewhere. Nothing here needs a code change on this PR.

_{🤖 Generated with Claude Code — automated CI triage; I can't build/run ClickHouse, so this is based on the praktika S3 reports and logs.}