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    SubjectRe: Analysis for Linux-2.5 fix/improve get_pid(), comparing various approaches
    Date
    On Friday 09 August 2002 12:05 pm, Linus Torvalds wrote:
    > On Fri, 9 Aug 2002, Hubertus Franke wrote:
    > > I dragged the various algorithms into a userlevel test program to figure
    > > out where the cut off points are with PID_MAX=32768. In this testprogram
    > > I maintain A tasks, and for 10 rounds (delete D random tasks and
    > > reallocate D tasks again) resulting in T=10*D total measured allocations.
    >
    > Mind re-doing that with PID_MAX=999999 or similar? The whole point of the
    > current simple algorithm is that the common case (nay, done right, the
    > _only_ case) is where the number of threads << PID_MAX.
    >

    Don't have time right now...
    Simply look at the numbers for the ratio you are expected.
    I would be very surprise if the relative curves would change
    when moving to 132K tasks and also populate the pid space only by
    let's say 25%.

    Otherwise, Paul can you run this....

    > That certainly used to be true with PID_MAX=32768 (not many people may
    > realize it, but in 1991 the maximum number of tasks in the system was
    > limited to 63, simply because of how the VM carved out the 4GB address
    > space).
    >
    > Things have changed, but considering that some people think that 32k
    > threads are a limitation already, and that the current code should work
    > fine (and be pretty much optimal) with a larger PID_MAX, I really think
    > it's unfair to not even benchmark that case..
    >
    > Linus

    --
    -- Hubertus Franke (frankeh@watson.ibm.com)
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