[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.
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