Expand description
Boot-timer — squib-internal latency device.
Per 14-virtio-and-devices.md § 4.8:
a trivial virtio device with no queues. The device exposes a 4-byte
config-space register at offset 0x100; on guest read, the register
returns (now_monotonic_ns − boot_start_ns) truncated to u32
microseconds (saturating at u32::MAX ≈ 71 minutes).
boot_start_ns is captured at the same point the kernel-load completes,
so the value the guest reads after init runs is “time from the moment
the kernel got control to the moment Linux first scheduled userspace.”
Used by the boot.rs criterion benchmark in
71-performance-budgets.md § 7.
Structs§
- Boot
Timer Device - virtio-boot-timer device.