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feat: --cpu-prof flags for CPU profiles#31909

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littledivy merged 9 commits intodenoland:mainfrom
littledivy:cpu-prof
Mar 9, 2026
Merged

feat: --cpu-prof flags for CPU profiles#31909
littledivy merged 9 commits intodenoland:mainfrom
littledivy:cpu-prof

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@littledivy littledivy commented Jan 21, 2026

This PR adds --cpu-prof, --cpu-prof-dir, --cpu-prof-md, --cpu-prof-name and --cpu-prof-interval

Example usage:

> target/debug/deno -A --cpu-prof --cpu-prof-md getrandom.js
> cat CPU.1769017882255.25986.md

# CPU Profile

| Duration | Samples | Interval | Functions |
| --- | --- | --- | --- |
| 833.06ms | 641 | 1000us | 10 |

**Top 10:** `op_crypto_get_random_values` 98.5%, `(garbage collector)` 0.7%, `getRandomValues` 0.6%, `assertBranded` 0.2%

## Hot Functions (Self Time)

| Self% | Self | Total% | Total | Function | Location |
| ---: | ---: | ---: | ---: | --- | --- |
| 98.5% | 533.00ms | 98.5% | 533.00ms | `op_crypto_get_random_values` | [native code] |
| 0.7% | 4.00ms | 0.7% | 4.00ms | `(garbage collector)` | [native code] |
| 0.6% | 3.00ms | 0.6% | 3.00ms | `getRandomValues` | 00_crypto.js:5274 |
| 0.2% | 1.00ms | 0.2% | 1.00ms | `assertBranded` | 00_webidl.js:1149 |

## Call Tree (Total Time)

| Total% | Total | Self% | Self | Function | Location |
| ---: | ---: | ---: | ---: | --- | --- |
| 16.8% | 91.00ms | 16.8% | 91.00ms | `(anonymous)` | server.js:1 |
| 0.6% | 3.00ms | 0.6% | 3.00ms |   `getRandomValues` | 00_crypto.js:5274 |
| 98.5% | 533.00ms | 98.5% | 533.00ms |     `op_crypto_get_random_values` | [native code] |
| 0.7% | 4.00ms | 0.7% | 4.00ms | `(garbage collector)` | [native code] |
| 0.0% | 0.00ms | 0.0% | 0.00ms | `dispatchLoadEvent` | 99_main.js:461 |
| 0.0% | 0.00ms | 0.0% | 0.00ms |   `dispatchEvent` | 02_event.js:1035 |
| 0.0% | 0.00ms | 0.0% | 0.00ms |     `assertBranded` | 00_webidl.js:1149 |

## Function Details

### `op_crypto_get_random_values`
[native code] | Self: 98.5% (533.00ms) | Total: 98.5% (533.00ms) | Samples: 533

### `(garbage collector)`
[native code] | Self: 0.7% (4.00ms) | Total: 0.7% (4.00ms) | Samples: 4

### `getRandomValues`
00_crypto.js:5274 | Self: 0.6% (3.00ms) | Total: 0.6% (3.00ms) | Samples: 3

### `assertBranded`
00_webidl.js:1149 | Self: 0.2% (1.00ms) | Total: 0.2% (1.00ms) | Samples: 1

kajukitli
kajukitli approved these changes Mar 7, 2026
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lgtm — nice feature addition for CPU profiling

the implementation is clean:

  • flags are well-structured with sensible defaults
  • CpuProfilerState uses inspector session to control V8's profiler
  • markdown report generation is a nice touch for quick analysis

the test coverage looks good with specs for basic usage, custom names, and md output

one minor thing: the --cpu-prof-interval default of 1000µs (1ms) is reasonable, but might want to document that higher values = less overhead but coarser resolution

@bartlomieju bartlomieju mentioned this pull request Mar 8, 2026
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kajukitli added a commit to kajukitli/docs that referenced this pull request Mar 8, 2026
@kajukitli
docs: add CPU profiling section to debugging page
3d9c4c5 
Documents the new --cpu-prof flags added in denoland/deno#31909:
- --cpu-prof: Enable CPU profiling
- --cpu-prof-dir: Output directory
- --cpu-prof-name: Custom filename
- --cpu-prof-interval: Sampling interval
- --cpu-prof-md: Generate Markdown report

Includes example of the Markdown report output format.
@kajukitli kajukitli mentioned this pull request Mar 8, 2026
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bartlomieju and others added 3 commits March 8, 2026 16:45
@bartlomieju @claude
refactor: consolidate cpu-prof flags into CpuProfFlags struct and add…
5295d5c 
… eval support

Move the 5 cpu-prof fields from RunFlags to a single CpuProfFlags struct
on the top-level Flags, making it easy to add cpu-prof to more subcommands.
Add --cpu-prof support to `deno eval` with a spec test.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@bartlomieju @claude
fix: address cpu-prof review feedback
237e0ef 
- Remove duplicate CpuProfConfig struct from cli/worker.rs, use
  CpuProfilerConfig from runtime everywhere
- Change cpu_prof_interval type from i32 to u32 (sampling interval
  can't be negative)
- Remove misleading Total columns from markdown report (they were
  identical to Self columns without proper descendant walking)
- Extract shared cpu_prof_filename() helper, eliminating duplicated
  timestamp/PID generation and unwrap() on SystemTime
- Always append worker ID to filename for web workers, even with
  custom --cpu-prof-name, preventing file overwrites
- Keep last two path segments in format_location() for better context
- Add --cpu-prof flags to deno serve subcommand
- Document that --cpu-prof-dir implicitly enables profiling
- Add explanatory comments for clippy allow and profile_msg_id race

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
@kajukitli
Merge main
2e1bba1
@littledivy littledivy requested a review from bartlomieju March 9, 2026 03:47
bartlomieju
bartlomieju approved these changes Mar 9, 2026
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Let's ship it

@littledivy littledivy merged commit 22258fb into denoland:main Mar 9, 2026
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bartlomieju added a commit that referenced this pull request Mar 14, 2026
@bartlomieju @claude
feat: add --cpu-prof-flamegraph to generate interactive SVG flamegrap…
e88d18a 
…hs (#32572)

## Summary

Builds on top of #31909 to add interactive SVG flamegraph generation for
CPU profiles, plus improvements to the existing `--cpu-prof`
functionality.

### New: `--cpu-prof-flamegraph` flag

Generates a self-contained, interactive SVG flamegraph alongside the
`.cpuprofile` file. No external dependencies required — the SVG is
generated directly from V8 CPU profile data.

```bash
deno run --cpu-prof --cpu-prof-flamegraph script.ts
# or
deno eval --cpu-prof --cpu-prof-flamegraph "/* code */"
```

**Flamegraph features:**
- Click any frame to zoom into that subtree
- "Reset Zoom" button to restore full view
- Ctrl+F / "Search" button for regex-based function search with magenta
highlighting and matched percentage
- "Invert" checkbox to flip into an icicle graph (root at top)
- Hover any frame to see function name and sample count in the status
bar
- Responsive — fills the browser viewport, adapts on resize
- Warm color gradient matching `cargo-flamegraph` / inferno style

### Other improvements
- **`deno eval` support**: All `--cpu-prof-*` flags now work with `deno
eval`
- **Fixed total time calculation**: The markdown report now properly
computes inclusive time (self + all descendants) using bottom-up tree
aggregation, instead of showing only self time

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
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@littledivy @bartlomieju @kajukitli