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Disk I/O bottlenecks in GitHub Actions
When your CI pipelines are slow, you can only optimize so much. Bottlenecks in CPU, Network, Memory, and Disk I/O can all contribute to slow CI pipelines. Let's take a look at how disk I/O can be a bottleneck in GitHub Actions.
GitHub offers different hosted-runners with a range of specs, but for this test we are using the default ubuntu-22.04 runner in a private repository, which does give us an additional 2 vCPUs but does not alter the disk performance. What we measured here aligns fairly closely with the 220MB/s we saw in the untar test, giving us another hint that we are likely being slowed down during our dependency installation, not by the network or CPU, but by the disk. Realistically, your disk performance will vary greatly depending on your specific cache size, the number of files, and just general build-to-build variance.
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