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    SubjectRe: [2.4.17/18pre] VM and swap - it's really unusable
    On Sun, Jan 13, 2002 at 01:11:21PM -0500, Robert Love wrote:
    > On Sun, 2002-01-13 at 10:18, jogi@planetzork.ping.de wrote:
    >
    > > No, I use a script which is run in single user mode after a reboot. So
    > > there are only a few processes running when I start the script (see
    > > attachment) and the jobs should start from the same environment.
    > >
    > > > What happens when you do the same test, compiling one kernel under multiple
    > > > different kernels?
    > >
    > > That is exactly what I am doing. I even try to my best to have the exact
    > > same starting environment ...
    >
    > So there you go, his testing is accurate. Now we have results that
    > preempt works and is best and it is still refuted. Everyone is running
    > around with these "ll is best" or "preempt sucks throughput" and that is

    assuming the report can be trusted this is not the test where we can
    measure a throughput regression, this is a VM intensive test and nothing
    else. Swap load.

    In short, run top and check you've 100% system load and cpus are never
    idle or in userspace, and _then_ it will most certainly get an interesting
    benchmark for -preempt throughput.

    Furthmore the whole comparison is flawed, just -O(1) is as broken as
    mainline w.r.t. the scheduling point, and -aa has the right scheduling
    point but not the -O(1) scheduler, so there's no way to compare those
    numbers at all. If you want to make any real comparison you should apply
    -preempt on top of -aa.

    Assuming it is really -preempt that makes the numbers more repetable
    (not the fact -O(1) alone has the broken rescheduling points), this
    still doesn't proof anything yet, the lower numbers are most certainly
    because those tasks getting the page faults get rescheduled faster, -aa
    didn't do more cpu work, it just had the cpus more idle than -preempt
    apparently, this may be the indication of an important scheduling point
    missing somewhere, if somebody could run a lowlatency measurement during
    a swap intensive load and send me the offending IP that could probably
    be addressed with a one liner.

    Andrea
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