RFC: Hiding per-CPU kernel output behind bootverbose

[Colin Percival]

On 04/19/18 13:44, Konstantin Belousov wrote:
> On Thu, Apr 19, 2018 at 06:06:21PM +0000, Colin Percival wrote:
>> On large systems (e.g., EC2's x1e.32xlarge instance type, with 128 vCPUs)
>> the boot time console output contains a large number of lines of the forms
>>
>> SMP: AP CPU #N Launched!
>> cpuN: <ACPI CPU> on acpi0
>> estN: <Enhanced SpeedStep Frequency Control> on cpuN
>>
>> Having 128 almost-identical lines of output doesn't seem very useful, and
>> it actually has a nontrivial impact on the time spent booting.
>>
>> Does anyone mind if I hide these by default, having them only show up if
>> boot verbosity is requested?
> 
> The 'CPU XX Launched' messages are very useful for initial diagnostic
> of the SMP startup failures. You need to enable bootverbose to see the
> hang details, but for initial hint they are required. Unfortunately, AP
> startup hangs occur too often to pretend that this can be delegated to
> very specific circumstances.

Do SMP startup failures need to be debugged often enough to justify having
this verbosity every time a FreeBSD system boots?

> Rest of the lines you pasted are normal device attach messages, so it is
> not clear how would you hide them without ugly hacks.

I would be willing to employ ugly hacks in order to silence unhelpful output
and speed up the boot process.

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid