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    SubjectRe: [Lse-tech] 7.52 second kernel compile
    On Sat, 16 Mar 2002, Martin J. Bligh wrote:

    > > I think Im addicted. I need help!
    >
    > Well, you're not going to get much competition, so maybe help
    > would be more in order ;-) ;-)
    >
    > Are you still doing something like this?
    > # MAKE="make -j14" /usr/bin/time make -j14 bzImage
    >
    > I tried setting the MAKE variable as well as doing the -j,
    > but it actually made kernel compile time slower - what difference
    > does it make on your machine? Can somebody clarify what this
    > actually does, as opposed to the -j on the command line?

    Passing the -j option to make either (a) starts N processes at the
    initial level and implies -j1 for submakes, (b) starts N processes at base
    level each of which get the -jN and use it, or (c) -jN means run a total
    of N processes shared between everything running. The [abc] depends on the
    make you run, BSD, xmake, old GNU, new GNU, etc.

    No that doesn't clarify things, the correct answer is "it depends." I
    have always used the environment variable with older GNU make, havent
    rethought it on very recent systems. I suggest that N be Nproc+1 for best
    results, but I've never had more than four CPUs with a build large enough
    to measure.

    > BTW - the other tip that was in the big book of whizzy kernel
    > compiles was to set gcc to use -pipe ... you might want to try
    > that.

    I general -pipe is a bad thing for uni, non-win for SMP (for any -j)
    although I have often thought that making the pipe buffer larger might
    change that.

    --
    bill davidsen <davidsen@tmr.com>
    CTO, TMR Associates, Inc
    Doing interesting things with little computers since 1979.

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