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    SubjectRe: Can and should the kernel HZ value be changed?

    On Wed, 6 Jan 1999, Pavel Machek wrote:

    > Linux has some problems with scheduling:
    > If you access disks or do other similar tasks (login), and there's
    > background process running, you get scheduled at next timer tick - ie.
    > 10ms later. This way, I was able to "feel" background while(1);
    > processes on my 486/16. I'm currently running some tests (find / in
    > fact), to see if this canbe measured in addition to 'felt'.

    no. you get scheduled immediately. You can 'feel' it with a background
    process running because starting up a shell is a multi-millisec CPU
    excercise even on fast boxes and fully cached, and processes do not start
    up with excessive priorities. (see how childs and parents share p->counter
    in fork.c) Thus the login is timesharing with the background process.

    but after a few seconds, your shell gathers enough 'interactiveness
    priority' to not hang when you hit 'Enter'.

    -- mingo

    ps. you can also renice the background process, in that case even right
    after fork() the typical shell process has higher priority than a CPU
    eater. 'renice' is your friend.

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