[Request for review] Profiling the FreeBSD kernel boot

Hans Petter Selasky hps at selasky.org
Fri Dec 22 13:51:28 UTC 2017

On 12/22/17 10:44, Colin Percival wrote:
> track down the
> places where we're wasting time during the boot, and then to fix them.


The USB stack will try to enumerate all USB controllers simultaneously.

DELAY() is frequently a problem having to wait for chips to reset during 
enumeration as you probably know. Getting timers enumerated early on 
allows to sleep instead of spin, also saving CPU usage during boot.

I'm not sure if switching on too many PCI devices at the same time can 
cause any power issues. At least USB HUBs have an own delay per port it 
needs to wait until power is turned on.


More information about the freebsd-current mailing list