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    SubjectRe: New fast(?)-boot results on ARM
    On 08/15/2009 12:35 AM, Zan Lynx wrote:
    > Linus Walleij wrote:
    >> 2009/8/14 Robert Schwebel <>:
    >>> On Fri, Aug 14, 2009 at 12:19:48PM -0600, Zan Lynx wrote:
    >>>>> That's factor 70 away from the 110 ms boot time Tim has talked about
    >>>>> some days ago (and he measured on an ARM cpu which had almost half
    >>>>> the speed of this one), and I'm wondering what we can do to improve
    >>>>> the boot time.
    >>>> 2.4s in uncompression? That seems like an obvious target for
    >>>> improvement.
    >>> Indeed, we'll check that.
    >> We got rid of uncompression on a flash-based system vastly improving
    >> boot time. The reason is that compressed kernels are faster only when
    >> the throughput to the persistent storage is lower than the decompression
    >> throughput, and on typical embedded systems with DMA the throughput to
    >> memory outperforms the CPU-based decompression.
    > I thought of another thing to check related to slow decompression. If
    > the kernel, bootloader or hardware is in charge of setting CPU power and
    > speed scaling, then you should check that it boots with the CPU set at
    > maximum speed instead of slowest.

    zlib is slow on decompression, and lzo is much faster. So if you implement
    lzo compression, you'll probably speed things up a little as well. I saw
    some discussions about this on lkml. Having no compression at all may also
    be a good thing to try.

    Best Regards,
    Artem Bityutskiy (Артём Битюцкий)
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