Date: Fri, 22 Dec 2017 22:05:11 +0800 From: blubee blubeeme <gurenchan@gmail.com> To: Colin Percival <cperciva@tarsnap.com> Cc: "freebsd-current@freebsd.org" <freebsd-current@freebsd.org> Subject: Re: [Request for review] Profiling the FreeBSD kernel boot Message-ID: <CALM2mEmLcHFsyNMMZPbyNRm_eVuoa17BxrgYBhfOFKwzVSaOYw@mail.gmail.com> 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 Fri, Dec 22, 2017 at 5:44 PM, Colin Percival <cperciva@tarsnap.com> wrote: > Hi everyone, > > For the past few months I've been working on code for profiling the FreeBSD > "kernel boot", i.e., everything between when kernel code starts running and > when we first enter userland as init(8). This is not trivial since it's > impossible to use tools like dtrace to monitor things prior to when said > tools are running. The goal of this exercise is to help me track down the > places where we're wasting time during the boot, and then to fix them. > > The approach I've taken is to add some macros -- most notably TSENTER() and > TSEXIT() -- which by default compile to nothing, but if the TSLOG kernel > option is enabled they compile to code which logs the cycle count (e.g., on > x86 the value from the RDTSC instruction) along with some other data (in > the > case of TSENTER and TSEXIT, the fact that we're entering/exiting a > function). > This can then be dumped via a sysctl (debug.tslog) and processed in > userland > to convert function entries/exits into stacks and to visualize the time > spent > in the boot process. > > Two examples: > > A flame chart of my laptop booting HEAD: > http://www.daemonology.net/timestamping/tslog-laptop.svg > > A flame chart of an EC2 c5.4xlarge instance booting 11.1-RELEASE: > http://www.daemonology.net/timestamping/tslog-c5.4xlarge.svg > > The patches (10 of them, to be applied in order), userland scripts, and > very > brief usage instructions are at: > http://www.daemonology.net/timestamping/tslog.tgz > > I hope to commit the patches in the next week, since I'm planning on > writing > a paper to submit to AsiaBSDCon (which has a deadline of December 31st); so > if anyone has interest/time to look at this in the near future (I mean, > it's > not like anyone is going to be busy this weekend, right?) I'd love to have > some feedback before it goes into the tree. > > -- > Colin Percival > Security Officer Emeritus, FreeBSD | The power to serve > Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid > _______________________________________________ > freebsd-current@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" > I've gotta say nice work with the tracing. Hopefully your talk gets accepted, i'd love to hear it.
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