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    SubjectRe: [PATCH v2] sched: Warn on long periods of pending need_resched
    On Wed, Mar 24, 2021 at 11:54:24AM +0100, Peter Zijlstra wrote:
    > On Wed, Mar 24, 2021 at 10:37:43AM +0100, Peter Zijlstra wrote:
    > > Should we perhaps take out all SCHED_DEBUG sysctls and move them to
    > > /debug/sched/ ? (along with the existing /debug/sched_{debug,features,preemp}
    > > files)
    > >
    > > Having all that in sysctl and documented gives them far too much sheen
    > > of ABI.
    >
    > ... a little something like this ...
    >

    I did not read this particularly carefully or boot it to check but some
    of the sysctls moved are expected to exist and should never should have
    been under SCHED_DEBUG.

    For example, I'm surprised that numa_balancing is under the SCHED_DEBUG
    sysctl because there are legimiate reasons to disable that at runtime.
    For example, HPC clusters running various workloads may disable NUMA
    balancing globally for particular jobs without wanting to reboot and
    reenable it when finished.

    Moving something like sched_min_granularity_ns will break a number of
    tuning guides as well as the "tuned" tool which ships by default with
    some distros and I believe some of the default profiles used for tuned
    tweak kernel.sched_min_granularity_ns

    Whether there are legimiate reasons to modify those values or not,
    removing them may generate fun bug reports.

    --
    Mel Gorman
    SUSE Labs

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