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    SubjectRe: Can context switches be faster?
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    Chris Friesen wrote:
    > John Richard Moser wrote:
    >
    >> Linux ported onto the L4-Iguana microkernel is reported to be faster
    >> than the monolith[1]; it's not like microkernels are faster, but the
    >> L4-Iguana apparently just has super awesome context switching code:
    >>
    >> Wombat's context-switching overheads as measured by lmbench on an
    >> XScale processor are up to thirty times less than those of native
    >> Linux, thanks to Wombat profiting from the implementation of fast
    >> context switches in L4-embedded.
    >
    > The Xscale is a fairly special beast, and it's context-switch times are
    > pretty slow by default.
    >
    > Here are some context-switch times from lmbench on a modified 2.6.10
    > kernel. Times are in microseconds:
    >
    > cpu clock speed context switch
    > pentium-M 1.8GHz 0.890
    > dual-Xeon 2GHz 7.430
    > Xscale 700MHz 108.2
    > dual 970FX 1.8GHz 5.850
    > ppc 7447 1GHz 1.720
    >
    > Reducing the Xscale time by a factor of 30 would basically bring it into
    > line with the other uniprocessor machines.
    >

    That's a load more descriptive :D

    0.890 uS, 0.556uS/cycle, that's barely 2 cycles you know. (Pentium M)
    PPC performs similarly, 1 cycle should be about 1uS.

    > Chris
    >

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