secret_freedom: Use fixed size bounce buffer for loading kernel #5203
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By using a MaybeBounce with N=0 we are allocating a bounce buffer that matches exactly the number of bytes that need to be copied into guest memory, e.g. the size of the kernel file. This is fairly expensive performance wise, and the spike in memory usage from the firecracker process is also unwanted. Thus, just use a 4096 byte fixed size buffer through which we repeatedly read+memcpy. Signed-off-by: Patrick Roy <[email protected]>
kalyazin
approved these changes
May 8, 2025
JackThomson2
approved these changes
May 8, 2025
roypat
merged commit c5eea10
into
firecracker-microvm:feature/secret-hiding
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By using a MaybeBounce with N=0 we are allocating a bounce buffer that matches exactly the number of bytes that need to be copied into guest memory, e.g. the size of the kernel file. This is fairly expensive performance wise, and the spike in memory usage from the firecracker process is also unwanted. Thus, just use a 4096 byte fixed size buffer through which we repeatedly read+memcpy. This has slightly better performance (10ms faster for cold boots) and makes Firecracker's memory usage during InstanceStart go back into its O(1) bound.
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CONTRIBUTING.md.PR Checklist
tools/devtool checkstyleto verify that the PR passes theautomated style checks.
how they are solving the problem in a clear and encompassing way.
in the PR.
CHANGELOG.md.Runbook for Firecracker API changes.
integration tests.
TODO.rust-vmm.