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… cleanup - Extract JIT region detection into standalone findJITRegion() function that handles both prctl-labeled mappings (spanning full reserved area including holes) and heuristic fallback (first anonymous executable mapping) - Add comprehensive unit tests for JIT region detection: no mappings, file-backed only, labeled single/multiple, heuristic fallback, precedence - Fix Detach() to clean up PidInterpreterMapping prefixes (previously only deleted proc data, leaking eBPF map entries) - Remove dead code: m.Vaddr < jitMapping.Vaddr branch that could never be true since /proc/pid/maps is sorted by address
- Fix JIT region check to use >= for lower bound (half-open interval [start, end)) matching V8 and HotSpot conventions - Reuse map lookup value to avoid double hashing of RawMapping struct key - Wrap CalculatePrefixList error for better debugging - Log stale prefix deletion errors instead of silently discarding - Move prctl(PR_SET_VMA) named anonymous mapping support from process/process.go (was in PR #36 but is needed here for findJITRegion labeled detection) - Remove stale 'assume all anonymous' comment - Rebuild BPF blobs for >= fix
- Add 'Register LPM prefixes' comment to SynchronizeMappings loop - Extract in_jit bool variable from inline if condition for clarity - Improve JIT detection comments (read_ruby_frame and walk_ruby_stack) - Fix whitespace: add blank line after FRAMES_PER_WALK_RUBY_STACK define, normalize MAX_EP_CHECKS spacing - Rebuild BPF blobs
Ruby 3.4.7 with --yjit on arm64. Verifies that: - JIT code region is detected from anonymous executable mappings - A JIT frame is pushed for the YJIT-compiled code - Ruby VM frames (is_prime, sum_of_primes, loop) are properly unwound after the JIT frame On main, this coredump fails with native_no_pid_page_mapping because the profiler doesn't know how to handle the anonymous JIT mapping. Moduledata tar for CI upload: ~/coredump-uploads/ruby-yjit-moduledata.tar
Ruby 3.4.7 with --yjit on x86_64. Same verification as arm64 test: - JIT code region detected from anonymous executable mappings - JIT frame pushed for YJIT-compiled code - Full Ruby VM stack unwound (is_prime, sum_of_primes, loop) Moduledata tar: ~/coredump-uploads/ruby-yjit-amd64-moduledata.tar
On systems with CONFIG_ANON_VMA_NAME=y, Ruby labels its JIT memory region via prctl(PR_SET_VMA), giving it a path like '[anon:Ruby:rb_yjit_reserve_addr_space]'. Without this fix, IsFileBacked() returns true for these mappings (non-empty Path), causing IsAnonymous() to return false. This prevents the LPM prefix registration loop in SynchronizeMappings from registering JIT executable pages for eBPF dispatch. Add IsPrctlNamed() helper and exclude prctl-named mappings from IsFileBacked(), so they are correctly classified as anonymous.
Co-authored-by: Florian Lehner <florianl@users.noreply.github.com>
Adapt SynchronizeMappings to work with uint32 values instead of *uint32 pointers: since generations are no longer shared via pointer, both mappings and their prefixes must be updated independently each cycle. Use an isNew flag to only call UpdatePidInterpreterMapping for newly discovered mappings.
Address florianl's concern about unlimited growth: entries are pruned each SynchronizeMappings call via generation tracking, and the map size is bounded by the number of executable anonymous mappings per process.
Only push the JIT frame when trace->num_frames == 0 (leaf position), restoring the original behavior. Without this guard, when native frames were already unwound before the Ruby unwinder runs, the JIT frame was pushed deep in the stack instead of at the leaf, causing it to appear as the root frame in flamegraphs.
This reverts commit f88aaa3.
walk_ruby_stack is re-entered via tail calls to process more frames. On re-entry, in_jit was recomputed from record->state.pc which hasn't changed (non-FP path), causing the JIT frame to be pushed again on every tail call. Guard with !jit_detected so the JIT frame is only pushed once on the first entry.
When the Ruby unwinder encounters a cfunc (C-implemented Ruby method), it normally transitions back to the native unwinder to unwind through the C code, then re-enters the Ruby unwinder when it detects the Ruby interpreter loop. Each such round-trip costs 2-3 tail calls out of a budget of 29, so a Ruby stack with 10+ cfuncs can easily truncate. This adds a skip_native_resume flag to RubyProcInfo that, when set, pushes cfunc frames inline without transitioning to the native unwinder. This trades native frames within cfuncs (e.g., the C call chain inside Array#sort) for complete Ruby-level traces without truncation. The flag is controlled by OTEL_EBPF_RUBY_SKIP_NATIVE_RESUME (default: false). Set to 'true' to enable.
- Correct inline comment that incorrectly stated 'Default to skipping' when the actual default is false (requires explicit opt-in) - Add note that skipNativeResume() is evaluated per-process at attach time
When skip_native_resume is true, the end-of-stack check should stop instead of resuming native unwinding. Without this, the native unwinder can re-enter the Ruby unwinder from JIT anonymous mappings, pushing frames in wrong positions.
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Summary
mainto upstreamopen-telemetry/opentelemetry-ebpf-profilermainat2e28aeaeb3a94b018e5db131550a78627bd056cf.89790045a02aed296e4f962db00b5c64edfa6da1dfe0d11d5929d8b5c1d9de473d9216033861cac6OTEL_EBPF_RUBY_SKIP_NATIVE_RESUMEbehaviorCurrent head:
e74cbe6dfd415c5349ee524af4df74771cfff7b5Validation
89790045a02aed296e4f962db00b5c64edfa6da1.dfe0d11d5929d8b5c1d9de473d9216033861cac6.e74cbe6dfd415c5349ee524af4df74771cfff7b5.env -u GOROOT -u GOTOOLCHAIN go test ./interpreter/ruby ./processdocker run --rm -v "$PWD":/work -w /work 07698be12d6c 'make -C support/ebpf lint'Profiles-processor bump PR: https://github.com/Shopify/profiles-processor/pull/1204
20e828d6dfca4c20273f66eabfa7d448fb8e786c.20e828d6dfca4c20273f66eabfa7d448fb8e786c.Production QA
Short
dev profileruns with prophiler image tag20e828d6dfca4c20273f66eabfa7d448fb8e786c/ image digestsha256:8dcf943c8bbd15f6e022905d232488234497b9f19310e9bd2952a65e21d19161.Queries are
native_profilesCPU scoped toprocess.executable.name="ruby"and each node.ERROR_4012: native_no_pid_page_mapping<unknown jit code>core-us-ce1b-sy3gke-core-us-ce1b-sy3-core-web-1-04315b31-2797ebpf-profiler-20260506-140535otherat 90.55% selfcore-us-ce1b-sy3gke-core-us-ce1b-sy3-core-web-1-04315b31-2d77OTEL_EBPF_RUBY_SKIP_NATIVE_RESUME=trueebpf-profiler-20260506-140633storefront-us-ce1b-tk2gke-storefront-us-ce-storefront-rende-75b8f29d-26cpebpf-profiler-20260506-140708storefront-us-ce1b-tk2gke-storefront-us-ce-storefront-rende-75b8f29d-2ml6OTEL_EBPF_RUBY_SKIP_NATIVE_RESUME=trueebpf-profiler-20260506-140742All Kubernetes jobs completed. The wide fallback continues to keep
ERROR_4012low versus the pre-fallback Core results (~10-11% self and ~72-96% total).