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fs: initialize subsystems lazily - #90
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Package init calls IsCgroup2HybridMode, which does statfs(2) on /sys/fs/cgroup/unified. This happens on every start of any program which imports this package (e.g. runc, including runc init), even when the fs cgroup manager is never used (as it is the case on cgroup v2 hosts). Make subsystems a sync.OnceValue to only do this when needed. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
AkihiroSuda
approved these changes
Oct 14, 2026
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Package init calls
IsCgroup2HybridMode, which doesstatfs(2)on/sys/fs/cgroup/unified. This happens on every start of any program which imports this package (e.g. runc, includingrunc init, which runs on every container start and exec), even when the fs cgroup manager is never used (as it is the case on cgroup v2 hosts).Make
subsystemsasync.OnceValueto only do this when needed.This saves about 6.6µs of init time per runc invocation (measured with
GODEBUG=inittrace=1).