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    Subject[PATCH 0/3] implement vcpu preempted check
    Date
    This is to fix some bad issues on an over-committed guest.

    test-caes:
    perf record -a perf bench sched messaging -g 400 -p && perf report

    18.09% sched-messaging [kernel.vmlinux] [k] osq_lock
    12.28% sched-messaging [kernel.vmlinux] [k] rwsem_spin_on_owner
    5.27% sched-messaging [kernel.vmlinux] [k] mutex_unlock
    3.89% sched-messaging [kernel.vmlinux] [k] wait_consider_task
    3.64% sched-messaging [kernel.vmlinux] [k] _raw_write_lock_irq
    3.41% sched-messaging [kernel.vmlinux] [k] mutex_spin_on_owner.is
    2.49% sched-messaging [kernel.vmlinux] [k] system_call

    osq takes a long time with preemption disabled which is really bad.

    This is because vCPU A hold the osq lock and yield out, vCPU B wait
    per_cpu node->locked to be set. IOW, vCPU B wait vCPU A to run and
    unlock the osq lock. Even there is need_resched(), it did not help on
    such scenario.

    we may also need fix other XXX_spin_on_owner later based on this patch set.
    these spin_on_onwer variant cause rcu stall.

    Pan Xinhui (3):
    powerpc/spinlock: support vcpu preempted check
    locking/osq: Drop the overload of osq_lock()
    kernel/sched: introduce vcpu preempted check interface

    arch/powerpc/include/asm/lppaca.h | 6 ++++++
    arch/powerpc/include/asm/spinlock.h | 15 +++++++++++++++
    include/linux/sched.h | 9 +++++++++
    kernel/locking/osq_lock.c | 16 +++++++++++++++-
    4 files changed, 45 insertions(+), 1 deletion(-)

    --
    2.4.11

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