Date: Fri, 22 Dec 2017 14:48:26 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Colin Percival <cperciva@tarsnap.com>, "freebsd-current@freebsd.org" <freebsd-current@freebsd.org> Subject: Re: [Request for review] Profiling the FreeBSD kernel boot Message-ID: <6d17d9f1-619e-98dd-d19f-7965171ea8fe@selasky.org> In-Reply-To: <010001607d9c59d5-15b6b788-a7ea-4edf-96e4-1235dd1a5c26-000000@email.amazonses.com> References: <010001607d9c59d5-15b6b788-a7ea-4edf-96e4-1235dd1a5c26-000000@email.amazonses.com>
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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. Hi, 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. --HPS
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