Add device_quiet_children() and device_has_quiet_children()

[imp]

Summary

If you add a child to a device that has quiet children, we'll
automatically set the quiet flag on the children.

This is indended for things like CPU that have a large amount of
repetition in booting.

Use device_quiet_children to silence verbose CPU probe messages.

Test Plan

boot and notice a lot fewer devices

[cperciva]

Works for me. Two minor questions about the code (see comments inline).

sys/dev/acpica/acpi_cpu.c

311

Is it intentional that cpu0 remains "noisy"? I don't object to this; but it's not quite what the summary says.

sys/kern/subr_bus.c

1832

Should we set device_quiet_children here too? I'd assume that if a device is so noisy that we want to quiet its children, we would also want to quiet its grandchildren.

[imp]

• Add device_quiet_children() and device_has_quiet_children()
• Use device_quiet_children to silence verbose CPU probe messages.
• Put the CPU starting on one line.

[cperciva]

Tested on EC2 x1.32xlarge (72 CPUs) and c5.18xlarge (128 CPUs) instances. Aside from making the console output far less verbose, the c5.18xlarge kernel boot time (measured from entering hammer_time to when init enters userland) dropped from 18.78 s to 11.75 s, and the x1.32xlarge kernel boot time dropped from 45.71 s to 36.33 s.

Please commit!

[imp]

43d9cb5b74fdb / r333334 landed this

sys/dev/acpica/acpi_cpu.c

311

Yes. It's intentional. It's what you proposed :)

sys/kern/subr_bus.c

1832

good point.