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    SubjectRe: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]
    William Lee Irwin III wrote:
    > * Andrew Morton <> wrote:
    >>> Yes, there are potential compatibility problems. Example: a machine
    >>> with 100 busy httpd processes and suddenly a big gzip starts up from
    >>> console or cron.
    > [...]
    > On Thu, Apr 19, 2007 at 08:38:10AM +0200, Ingo Molnar wrote:
    >> hmmmm. How about the following then: default to nice -10 for all
    >> (SCHED_NORMAL) kernel threads and all root-owned tasks. Root _is_
    >> special: root already has disk space reserved to it, root has special
    >> memory allocation allowances, etc. I dont see a reason why we couldnt by
    >> default make all root tasks have nice -10. This would be instantly loved
    >> by sysadmins i suspect ;-)
    >> (distros that go the extra mile of making Xorg run under non-root could
    >> also go another extra one foot to renice that X server to -10.)
    > I'd further recommend making priority levels accessible to kernel threads
    > that are not otherwise accessible to processes, both above and below
    > user-available priority levels. Basically, if you can get SCHED_RR and
    > SCHED_FIFO to coexist as "intimate scheduler classes," then a SCHED_KERN
    > scheduler class can coexist with SCHED_OTHER in like fashion, but with
    > availability of higher and lower priorities than any userspace process
    > is allowed, and potentially some differing scheduling semantics. In such
    > a manner nonessential background processing intended not to ever disturb
    > userspace can be given priorities appropriate to it (perhaps even con's
    > SCHED_IDLEPRIO would make sense), and other, urgent processing can be
    > given priority over userspace altogether.
    > I believe root's default priority can be adjusted in userspace as
    > things now stand somewhere in /etc/ but I'm not sure of the specifics.
    > Word is somewhere in /etc/security/limits.conf

    This is sounding very much like System V Release 4 (and descendants)
    except that they call it SCHED_SYS and also give SCHED_NORMAL tasks that
    are in system mode dynamic priorities in the SCHED_SYS range (to avoid
    priority inversion, I believe).

    Peter Williams

    "Learning, n. The kind of ignorance distinguishing the studious."
    -- Ambrose Bierce
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