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    Subjectparallel boot device initialisation (kernel-space not userspace)
    hello darlings,

    well i actually followed the FAQ
    on this one, and got to try 'do a search' bit, and when searches
    for 'parallel boot initialisation' came up with discussions about
    parallel ports, and articles on ibm developerworks about sysvinit,
    i made the decision to post this anyway.

    I Have A Great Idea(tm) and would like to describe it concisely
    to see if anyone likes it and hopefully hasn't thought of it before
    so i'm not consuming people's time.

    The idea is: parallel device initialisation of built-in modules, to
    reduce kernel boot time.

    parallel initialisation is taken care of in user-space by modifying
    udev coldplug scripts to watch subsets of the /sys/class/*/event
    files disappearing, and by using things like depinit, startpar for
    suse, gentoo's parallel startup system (inspired by depinit)

    .. but is there _anything_ like this actually in the linux kernel

    i don't believe so, and the reasoning i base that on is that when
    i boot my devices (be it a pc or be it an HTC smartphone device
    i'm helping to reverse-engineer) the kernel startup log is always
    the same, and that multiple messages coming from the same device
    (printks) are always grouped together.

    i realise that that's slightly faulty reasoning: it could
    be that device initialisation is so regular like clockwork that
    the output is always the same...


    now i have to try some things, as an experiment. and i would
    like to start with asic3 platform_device, because it contains
    dynamically-created lists of child devices and so is a model
    example of the kind of dependency-hierarchy that's needed.

    so, i seek people's advice on this rather naive approach: simply
    set up a workqueue and call schedule_work() on each of the asic3
    child platform_devices.

    does that sound reasonable, or is it just too simplistic?


    p.s. see last few lines of asic3_probe, here, where
    platform_add_devices() is called:

    p.p.s. whilst my 1.2ghz fujitsu laptop (debian/unstable) with depinit
    takes only 20 seconds to get from 1st process being run (/sbin/depinit)
    to xorg running, it takes ANOTHER 20 seconds to get from kernel boot
    up to 1st process (/sbin/depinit) ! that's with a standard debian
    kernel - hence my interest in cutting that time to ... well...
    under 5 seconds would be nice.

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      Last update: 2006-12-08 17:37    [W:0.023 / U:14.660 seconds]
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