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neon/safekeeper/benches/README.md
Erik Grinaker 190e8cebac safekeeper,pageserver: add CPU profiling (#9764)
## Problem

We don't have a convenient way to gather CPU profiles from a running
binary, e.g. during production incidents or end-to-end benchmarks, nor
during microbenchmarks (particularly on macOS).

We would also like to have continuous profiling in production, likely
using [Grafana Cloud
Profiles](https://grafana.com/products/cloud/profiles-for-continuous-profiling/).
We may choose to use either eBPF profiles or pprof profiles for this
(pending testing and discussion with SREs), but pprof profiles appear
useful regardless for the reasons listed above. See
https://github.com/neondatabase/cloud/issues/14888.

This PR is intended as a proof of concept, to try it out in staging and
drive further discussions about profiling more broadly.

Touches #9534.
Touches https://github.com/neondatabase/cloud/issues/14888.

## Summary of changes

Adds a HTTP route `/profile/cpu` that takes a CPU profile and returns
it. Defaults to a 5-second pprof Protobuf profile for use with e.g.
`pprof` or Grafana Alloy, but can also emit an SVG flamegraph. Query
parameters:

* `format`: output format (`pprof` or `svg`)
* `frequency`: sampling frequency in microseconds (default 100)
* `seconds`: number of seconds to profile (default 5)

Also integrates pprof profiles into Criterion benchmarks, such that
flamegraph reports can be taken with `cargo bench ... --profile-duration
<seconds>`. Output under `target/criterion/*/profile/flamegraph.svg`.

Example profiles:

* pprof profile (use [`pprof`](https://github.com/google/pprof)):
[profile.pb.gz](https://github.com/user-attachments/files/17756788/profile.pb.gz)
  * Web interface: `pprof -http :6060 profile.pb.gz`
* Interactive flamegraph:
[profile.svg.gz](https://github.com/user-attachments/files/17756782/profile.svg.gz)
2024-11-21 18:59:46 +00:00

809 B

Safekeeper Benchmarks

To run benchmarks:

# All benchmarks.
cargo bench --package safekeeper

# Specific file.
cargo bench --package safekeeper --bench receive_wal

# Specific benchmark.
cargo bench --package safekeeper --bench receive_wal process_msg/fsync=false

# List available benchmarks.
cargo bench --package safekeeper --benches -- --list

# Generate flamegraph profiles using pprof-rs, profiling for 10 seconds.
# Output in target/criterion/*/profile/flamegraph.svg.
cargo bench --package safekeeper --bench receive_wal process_msg/fsync=false --profile-time 10

Additional charts and statistics are available in target/criterion/report/index.html.

Benchmarks are automatically compared against the previous run. To compare against other runs, see --baseline and --save-baseline.