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    SubjectRe: [RFC][PATCH 00/16] sched: Core scheduling
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    On 2/21/19 6:03 AM, Peter Zijlstra wrote:
    > On Wed, Feb 20, 2019 at 06:53:08PM -0800, Subhra Mazumdar wrote:
    >> On 2/18/19 9:49 AM, Linus Torvalds wrote:
    >>> On Mon, Feb 18, 2019 at 9:40 AM Peter Zijlstra <peterz@infradead.org> wrote:
    >>>> However; whichever way around you turn this cookie; it is expensive and nasty.
    >>> Do you (or anybody else) have numbers for real loads?
    >>>
    >>> Because performance is all that matters. If performance is bad, then
    >>> it's pointless, since just turning off SMT is the answer.
    >>>
    >>> Linus
    >> I tested 2 Oracle DB instances running OLTP on a 2 socket 44 cores system.
    >> This is on baremetal, no virtualization.
    > I'm thinking oracle schedules quite a bit, right? Then you get massive
    > overhead (as shown).
    Yes. In terms of idleness we have:

    Users baseline core_sched
    16    67% 70%
    24    53% 59%
    32    41% 49%

    So there is more idleness with core sched which is understandable as there
    can be forced idleness. The other part contributing to regression is most
    likely overhead.
    >
    > The thing with virt workloads is that if they don't VMEXIT lots, they
    > also don't schedule lots (the vCPU stays running, nested scheduler
    > etc..).
    I plan to run some VM workloads.
    >
    > Also; like I wrote, it is quite possible there is some sibling rivalry
    > here, which can cause excessive rescheduling. Someone would have to
    > trace a workload and check.
    >
    > My older patches had a condition that would not preempt a task for a
    > little while, such that it might make _some_ progress, these patches
    > don't have that (yet).
    >

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