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Add maxperf build profile (#3608)

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## Proposed Changes

Add a new Cargo compilation profile called `maxperf` which enables more aggressive compiler optimisations at the expense of compilation time.

Some rough initial benchmarks show that this can provide up to a 25% reduction to run time for CPU bound tasks like block processing: https://docs.google.com/spreadsheets/d/15jHuZe7lLHhZq9Nw8kc6EL0Qh_N_YAYqkW2NQ_Afmtk/edit

The numbers in that spreadsheet compare the `consensus-context` branch from #3604 to the same branch compiled with the `maxperf` profile using:

```
PROFILE=maxperf make install-lcli
```

## Additional Info

The downsides of the maxperf profile are:

- It increases compile times substantially, which will particularly impact low-spec hardware. Compiling `lcli` is about 3x slower. Compiling Lighthouse is about 5x slower on my 5950X: 17m 38s rather than 3m 28s.

As a result I think we should not enable this everywhere by default.

- **Option 1**: enable by default for our released binaries. This gives the majority of users the fastest version of `lighthouse` possible, at the expense of slowing down our release CI. Source builds will continue to use the default `release` profile unless users opt-in to `maxperf`.
- **Option 2**: enable by default for source builds. This gives users building from source an edge, but makes them pay for it with compilation time. 

I think I would prefer Option 1. I'll try doing some benchmarking to see how long a maxperf build of Lighthouse would take on GitHub actions.

Credit to Nicholas Nethercote for documenting these options in the Rust Performance Book: https://nnethercote.github.io/perf-book/build-configuration.html.
This commit is contained in:
Michael Sproul
2022-09-29 06:13:33 +00:00
parent 8d325e700b
commit f77e3bc0ad
6 changed files with 69 additions and 21 deletions
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21
book/src/installation-source.md
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@@ -120,7 +120,7 @@ You can customise the features that Lighthouse is built with using the `FEATURES
variable. E.g.
```
env FEATURES="gnosis,slasher-lmdb" make
FEATURES=gnosis,slasher-lmdb make
```
Commonly used features include:
@@ -131,6 +131,25 @@ Commonly used features include:
* `slasher-mdbx`: support for the MDBX slasher backend (enabled by default).
* `slasher-lmdb`: support for the LMDB slasher backend.
## Compilation Profiles
You can customise the compiler settings used to compile Lighthouse via
[Cargo profiles](https://doc.rust-lang.org/cargo/reference/profiles.html).
Lighthouse includes several profiles which can be selected via the `PROFILE` environment variable.
* `release`: default for source builds, enables most optimisations while not taking too long to
compile.
* `maxperf`: default for binary releases, enables aggressive optimisations including full LTO.
Although compiling with this profile improves some benchmarks by around 20% compared to `release`,
it imposes a _significant_ cost at compile time and is only recommended if you have a fast CPU.
To compile with `maxperf`:
```
PROFILE=maxperf make
```
## Troubleshooting
### Command is not found