feat: add --memory-track-physical experimental flag

[not-matthias]

What

Adds an experimental --memory-track-physical flag to codspeed run and codspeed exec. When set, it forwards CODSPEED_MEMTRACK_TRACK_PHYSICAL=1 to the memtrack subprocess, enabling the rss_stat tracepoint plus the folio rmap hooks for physical (resident) memory reconstruction.

Why

memtrack already gates this behind the CODSPEED_MEMTRACK_TRACK_PHYSICAL env var (crates/memtrack/src/ebpf/tracker.rs), inherited implicitly by the subprocess. This adds a discoverable, documented CLI flag under the Experimental heading (with the standard experimental-flag warning banner), while keeping the underlying env var identical so standalone memtrack usage is unaffected.

Implementation

• ExperimentalArgs::experimental_memory_track_physical (--memory-track-physical, env CODSPEED_MEMTRACK_TRACK_PHYSICAL), using FalseyValueParser so the env var's 1 value parses correctly (clap's default bool parser only accepts true/false).
• Threaded through OrchestratorConfig / ExecutorConfig alongside the existing valgrind experimental flags (fair_sched, etc.).
• MemoryExecutor::build_memtrack_command sets CODSPEED_MEMTRACK_TRACK_PHYSICAL=1 on the memtrack subprocess's environment when the flag is enabled. Default (off) behavior is unchanged, and a user-exported env var still works exactly as before (no CLI flag required).

Verification

• cargo check --workspace --all-targets, cargo fmt --check, cargo clippy --all-targets all clean.
• cargo test --release -p codspeed-runner --lib — all cli/config tests pass (the only failures are pre-existing sudo-gated walltime/valgrind tests unrelated to this change, failing on this box due to no passwordless sudo).
• Manually verified via codspeed exec --mode memory:
  • --memory-track-physical prints the experimental warning banner.
  • CODSPEED_MEMTRACK_TRACK_PHYSICAL=1 (matching memtrack's own convention) also enables it.
  • Omitting both leaves the flag off (default).

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 17 untouched benchmarks

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_{Comparing cod-3500-expose-rss-physical-memory-tracking-via-experimental-flag (ebc51da) with main (a4bd056)}

[greptile-apps]

Greptile Summary

Adds an experimental physical-memory tracking option for memory-mode executions.

• Propagates the parsed setting through orchestrator and executor configuration.
• Sets CODSPEED_MEMTRACK_TRACK_PHYSICAL=1 on the memtrack subprocess when enabled.
• Adds the option to experimental-feature warnings, but currently exposes a different CLI name than the documented interface.

Confidence Score: 4/5

The PR is not safe to merge until the implemented CLI option matches the advertised --memory-track-physical interface.

The recent naming change makes clap expose --experimental-memory-track-physical, so invoking the documented option fails before physical tracking can be enabled. The earlier tracker-version thread was manually resolved after not-matthias stated that a supporting release would be available soon and therefore is not treated as outstanding.

Files Needing Attention: src/cli/experimental.rs

Important Files Changed

Filename	Overview
src/cli/experimental.rs	Defines and reports the experimental option, but derives a CLI name that differs from the advertised --memory-track-physical interface.
src/cli/run/mod.rs	Correctly forwards the parsed physical-memory setting for run.
src/cli/exec/mod.rs	Correctly forwards the parsed physical-memory setting for exec.
src/executor/config.rs	Carries the setting from run-level configuration into each execution context.
src/executor/memory/executor.rs	Conditionally sets the fixed memtrack environment variable before launching the tracker.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart LR
    CLI["run / exec flag or environment"] --> OA["OrchestratorConfig"]
    OA --> EC["ExecutorConfig"]
    EC --> ME["MemoryExecutor"]
    ME --> ENV["CODSPEED_MEMTRACK_TRACK_PHYSICAL=1"]
    ENV --> MT["codspeed-memtrack"]

Loading

Prompt To Fix All With AI

### Issue 1
src/cli/experimental.rs:22
**Advertised flag is unavailable**

The bare `long` derives `--experimental-memory-track-physical` from the field name, while this feature is advertised as `--memory-track-physical`. Users who invoke the advertised option receive an unknown-argument error instead of enabling physical memory tracking. The warning text at line 47 also uses the derived name, so the public option and warning should both be kept aligned with the advertised interface.

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For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (2): Last reviewed commit: "fix: silence dead-code lint on non-Linux..." | Re-trigger Greptile}