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CI: optimize ext4 mount options that can be toggled at runtime. #148085

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CI: optimize ext4 mount options that can be toggled at runtime. #148085

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8b4c648
optimize ext4 mount options that can be toggled at runtime.
the8472 Oct 25, 2025
7b2545a
run iostat while freeing up disk space
the8472 Oct 26, 2025
964c658
parallel delete
the8472 Oct 26, 2025
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3 changes: 3 additions & 0 deletions .github/workflows/ci.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -117,6 +117,9 @@ jobs:
with:
fetch-depth: 2

- name: remount root filesystem
run: src/ci/scripts/tune-rootfs.sh

# Free up disk space on Linux by removing preinstalled components that
# we do not need. We do this to enable some of the less resource
# intensive jobs to run on free runners, which however also have
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12 changes: 10 additions & 2 deletions src/ci/scripts/free-disk-space-linux.sh
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Expand Up @@ -173,8 +173,11 @@ removeUnusedFilesAndDirs() {
fi
done

# Remove all files and directories at once to save time.
sudo rm -rf "${to_remove[@]}"
# GHA has high read latencies for uncached data
# so we traverse directories in parallel and feed the output to rm
printf '%s\n' "${to_remove[@]}" | \
(xargs -P 6 -I{} -- find {} -type f -printf '%p\n\c' || true) | \
sudo xargs -r -P 8 -n 100 -- rm -rf
}

execAndMeasureSpaceChange() {
Expand Down Expand Up @@ -253,11 +256,16 @@ AVAILABLE_INITIAL=$(getAvailableSpace)

printDF "BEFORE CLEAN-UP:"
echo ""

iostat -x 20 &

execAndMeasureSpaceChange cleanPackages "Unused packages"
execAndMeasureSpaceChange cleanDocker "Docker images"
execAndMeasureSpaceChange cleanSwap "Swap storage"
execAndMeasureSpaceChange removeUnusedFilesAndDirs "Unused files and directories"

kill %1

# Output saved space statistic
echo ""
printDF "AFTER CLEAN-UP:"
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25 changes: 25 additions & 0 deletions src/ci/scripts/tune-rootfs.sh
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@@ -0,0 +1,25 @@
#!/bin/bash

set -euo pipefail
IFS=$'\n\t'

source "$(cd "$(dirname "$0")" && pwd)/../shared.sh"

if isLinux && [[ $(findmnt -n /) =~ "ext4" ]] ; then
# noauto_da_alloc since auto_da_alloc causes sync IO for some common file creation patterns
# lazytime avoids sync IO when (rel)atime updates are applied
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Is it possible to use noatime here?

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Deleting stuff doesn't just update atime but also ctime and mtime, so I don't think noatime would make a difference here.

Anyway, the settings don't seem to make much of a difference, so this might not be due to sync-write-latency but due to read latency (enumerating the directories) or just being IOPS-starved (anemic cloud hardware).
I'll try running iostat alongside the deletion.

# barrier=0 disables write cache flushing, which can reduce latency at the cost of durability,
# but CI machines are ephemeral, so we don't need to be crash-proof.
#
# Ideally we'd set additional options, but those would require
# a reboot or unmounting the rootfs.
sudo mount -oremount,delalloc,lazytime,barrier=0,noauto_da_alloc /
sudo bash -c 'echo "write through" > /sys/block/sda/queue/write_cache' || true
sudo bash -c 'echo "write through" > /sys/block/sdb/queue/write_cache' || true

ionice -c 3 fstrim / &

lsblk

mount
fi
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