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  • Re: swapping pain, Why I've Dropped In

    From John Levine@21:1/5 to All on Sun Jun 15 17:39:23 2025
    According to Stephen Fuld <sfuld@alumni.cmu.edu.invalid>:
    like" functionality and the resulting overhead. IIRC the site specified
    the size and number of user areas within TSO, and users competed for one
    of those. It may be (I don't remember) that once a user program was
    assigned to a user slot, if it got swapped out (by the TSO program), it
    had to be swapped back into the same user area. This eliminated the >relocation problem we have been discussing. It was very slow with even
    a few users.

    Even without TSO, OS/360 had a feature called rollout/rollin which
    swapped out a lower priority job to allow a higher priority one to use
    more storage, then swapped it back in to the same place. I don't think
    it was very popular.
    --
    Regards,
    John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
    Please consider the environment before reading this e-mail. https://jl.ly

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  • From Stephen Fuld@21:1/5 to John Levine on Sun Jun 15 12:23:14 2025
    On 6/15/2025 10:39 AM, John Levine wrote:
    According to Stephen Fuld <sfuld@alumni.cmu.edu.invalid>:
    like" functionality and the resulting overhead. IIRC the site specified
    the size and number of user areas within TSO, and users competed for one
    of those. It may be (I don't remember) that once a user program was
    assigned to a user slot, if it got swapped out (by the TSO program), it
    had to be swapped back into the same user area. This eliminated the
    relocation problem we have been discussing. It was very slow with even
    a few users.

    Even without TSO, OS/360 had a feature called rollout/rollin which
    swapped out a lower priority job to allow a higher priority one to use
    more storage, then swapped it back in to the same place. I don't think
    it was very popular.

    Agreed. I think its lack of popularity was due to the requirement that
    the (batch) program be rolled back in to the same physical location as
    it was rolled out of. For batch programs, it seems hard to find a good
    use case for this.

    But TSO was for interactive programs, so swapping out one interactive
    user while the user was "thinking" and letting another user use the CPU
    and memory for that multiple seconds seems like a good idea.


    --
    - Stephen Fuld
    (e-mail address disguised to prevent spam)

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