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Try to avoid fuzz disk fullness #3916

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Merged
merged 3 commits into from
Jul 9, 2025
Merged

Try to avoid fuzz disk fullness #3916

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d33a1d1
Clean `apt` package cache ASAP to safe some disk space
tnull Jul 8, 2025
f0ec19d
Run `cargo clean` after `write-seeds` step
tnull Jul 8, 2025
f6238fc
Keep `codegen-units = 1` for CI fuzzing
tnull Jul 8, 2025
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3 changes: 3 additions & 0 deletions .github/workflows/build.yml
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Expand Up @@ -49,10 +49,12 @@ jobs:
run: |
rustup target add thumbv7m-none-eabi
sudo apt-get -y install gcc-arm-none-eabi
sudo apt-get clean
- name: shellcheck the CI and `contrib` scripts
if: "matrix.platform == 'ubuntu-latest'"
run: |
sudo apt-get -y install shellcheck
sudo apt-get clean
shellcheck ci/*.sh -aP ci
shellcheck contrib/*.sh -aP contrib
- name: Set RUSTFLAGS to deny warnings
Expand Down Expand Up @@ -260,6 +262,7 @@ jobs:
run: |
sudo apt-get update
sudo apt-get -y install build-essential binutils-dev libunwind-dev
sudo apt-get clean
- name: Pin the regex dependency
run: |
cd fuzz && cargo update -p regex --precise "1.9.6" --verbose
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5 changes: 3 additions & 2 deletions fuzz/ci-fuzz.sh
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Expand Up @@ -18,13 +18,14 @@ export RUSTFLAGS="--cfg=secp256k1_fuzz --cfg=hashes_fuzz"
mkdir -p hfuzz_workspace/full_stack_target/input
pushd write-seeds
RUSTFLAGS="$RUSTFLAGS --cfg=fuzzing" cargo run ../hfuzz_workspace/full_stack_target/input
cargo clean
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Shouldn't we really not add a du in here to see what needs cleaning and what doesn't? Also to not unnecessarily increase build times.

And can the disk space in github be increased?

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Shouldn't we really not add a du in here to see what needs cleaning and what doesn't? Also to not unnecessarily increase build times.

Huh, we only clean up here and below once were done? So should not have ~any overhead to clean target dirs that you aren't using anymore?

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I thought it would lead to re-downloads of packages. Not that would matter much even if it was the case with a 4h job...

popd

cargo install --color always --force honggfuzz --no-default-features

# Because we're fuzzing relatively few iterations, the maximum possible
# compiler optimizations aren't necessary, so switch to defaults.
# compiler optimizations aren't necessary, so we turn off LTO
sed -i 's/lto = true//' Cargo.toml
sed -i 's/codegen-units = 1//' Cargo.toml
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Removing this is likely to slow the build step down substantially.

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Removing this is likely to slow the build step down substantially.

Which part do you mean exactly. As mentioned below, lto was never used as it conflicts with codegen-units = 1.

With the sed commands above, we would fallback to defaults in CI, meaning lto = false (see https://doc.rust-lang.org/cargo/reference/profiles.html#dev), and codegen-units = 16. Do we expect the latter to make that much of an impact?

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Yes, the build step takes a minute, and making it single-threaded is unlikely to help :). It may be okay because we can parallelize across binaries, but no reason to slow it down more.

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Hmm, I guess we'll have the benchmark for comparison in a bit. Let's see how long it will take.

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@tnull tnull Jul 9, 2025 •
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The fuzz job on this branch finished in ~4h 20m. Looking at recent examples of PRs where the CI used to pass, it did so in ~4h 15m. I think 5 min/2% difference is acceptable?

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@tnull tnull Jul 9, 2025 •
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Ah, 4h 13m this time around, so we even have some speedup compared to some recent PRs I looked at. Seems the variance in CI is larger than the impact of the actual change.

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Alright, yea, then the cross-binary parallelization dominates. Cool. Its less clear to me if this makes a difference on disk space usage, but it doesn't really matter.


export HFUZZ_BUILD_ARGS="--features honggfuzz_fuzz"

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