jailer: fix perf regression when closing open FDs #3595
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Fixes the mechanism for closing open FDs in jailer which was based on the SC_OPEN_MAX system constant. Such an approach can lead to bad performance when this value is very high. The method for closing file descriptors is now chosen based on the environment: 1. we try to call into the close_range syscall (available on kernels >=5.9) 2. we fallback to reading from /proc/self/fd (for kernels <5.9) Fixes firecracker-microvm#3542. Signed-off-by: Grzegorz Uriasz <gorbak25@gmail.com> Co-authored-by: Diana Popa <dpopa@amazon.com>
Signed-off-by: Diana Popa <dpopa@amazon.com>
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Status: Awaiting review
roypat
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Apr 12, 2023
Signed-off-by: Diana Popa <dpopa@amazon.com>
roypat
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Apr 13, 2023
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Apr 13, 2023
andreitraistaru
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Apr 13, 2023
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Changes
Fixes the mechanism for closing open FDs in jailer which was
based on the SC_OPEN_MAX system constant. Such an approach can lead
to bad performance when this value is very high.
The method for closing file descriptors is now chosen based on the environment:
Reason
Fixes #3542 - a bug where firecracker would end up spending minutes starting which arises when running on systems with OPEN_MAX set to a very high number.
Thanks @gorbak25 for reporting the issue and proposing the fix!
License Acceptance
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CONTRIBUTING.md.PR Checklist
CHANGELOG.md.TODOs link to an issue.rust-vmm.