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    SubjectRe: Runtime overhead of PREEMPT_DYNAMIC
    Hi Mike,

    On 2023-10-20 02:42, Mike Galbraith wrote:
    > It's kinda hard to imagine the author's mailbox surviving submission
    > day were it _that_ horrid, surely something is amiss.

    Thanks for trying to reproduce! Let's see if we can find out what's
    wrong in my setup then.

    > voluntary (my usual)
    > CONFIG_PREEMPT_VOLUNTARY_BUILD=y
    > # CONFIG_PREEMPT_NONE is not set
    > CONFIG_PREEMPT_VOLUNTARY=y
    > # CONFIG_PREEMPT is not set
    > # CONFIG_PREEMPT_DYNAMIC is not set
    >
    > dynamic (same config, just flip dynamic switch)
    > CONFIG_PREEMPT_BUILD=y
    > # CONFIG_PREEMPT_NONE is not set
    > CONFIG_PREEMPT_VOLUNTARY=y
    > # CONFIG_PREEMPT is not set
    > CONFIG_PREEMPT_COUNT=y
    > CONFIG_PREEMPTION=y
    > CONFIG_PREEMPT_DYNAMIC=y

    Here is the full diff between the kernel configurations I used. The only
    change I made was setting CONFIG_PREEMPT_DYNAMIC=n, everything else was
    a consequence of that AFAICT, but please do let me know if you see
    anything that shouldn't be there.

    --- config-6.5.0-0.preempt-dynamic-amd64 2023-10-11 15:30:02.000000000 +0200
    +++ config-6.5.0-0.a.test-amd64 2023-10-11 14:30:02.000000000 +0200
    @@ -125,13 +125,11 @@
    CONFIG_BPF_LSM=y
    # end of BPF subsystem

    -CONFIG_PREEMPT_BUILD=y
    +CONFIG_PREEMPT_VOLUNTARY_BUILD=y
    # CONFIG_PREEMPT_NONE is not set
    CONFIG_PREEMPT_VOLUNTARY=y
    # CONFIG_PREEMPT is not set
    -CONFIG_PREEMPT_COUNT=y
    -CONFIG_PREEMPTION=y
    -CONFIG_PREEMPT_DYNAMIC=y
    +# CONFIG_PREEMPT_DYNAMIC is not set
    # CONFIG_SCHED_CORE is not set

    #
    @@ -156,11 +154,9 @@
    # RCU Subsystem
    #
    CONFIG_TREE_RCU=y
    -CONFIG_PREEMPT_RCU=y
    # CONFIG_RCU_EXPERT is not set
    CONFIG_TREE_SRCU=y
    CONFIG_TASKS_RCU_GENERIC=y
    -CONFIG_TASKS_RCU=y
    CONFIG_TASKS_RUDE_RCU=y
    CONFIG_TASKS_TRACE_RCU=y
    CONFIG_RCU_STALL_COMMON=y
    @@ -1009,7 +1005,11 @@
    CONFIG_PREEMPT_NOTIFIERS=y
    CONFIG_PADATA=y
    CONFIG_ASN1=y
    -CONFIG_UNINLINE_SPIN_UNLOCK=y
    +CONFIG_INLINE_SPIN_UNLOCK_IRQ=y
    +CONFIG_INLINE_READ_UNLOCK=y
    +CONFIG_INLINE_READ_UNLOCK_IRQ=y
    +CONFIG_INLINE_WRITE_UNLOCK=y
    +CONFIG_INLINE_WRITE_UNLOCK_IRQ=y
    CONFIG_ARCH_SUPPORTS_ATOMIC_RMW=y
    CONFIG_MUTEX_SPIN_ON_OWNER=y
    CONFIG_RWSEM_SPIN_ON_OWNER=y
    @@ -5395,7 +5395,6 @@
    CONFIG_MEDIA_CEC_SUPPORT=y
    # CONFIG_CEC_CH7322 is not set
    # CONFIG_CEC_CROS_EC is not set
    -# CONFIG_CEC_GPIO is not set
    CONFIG_CEC_SECO=m
    # CONFIG_CEC_SECO_RC is not set
    CONFIG_USB_PULSE8_CEC=m
    @@ -10597,7 +10596,6 @@
    # end of Scheduler Debugging

    # CONFIG_DEBUG_TIMEKEEPING is not set
    -CONFIG_DEBUG_PREEMPT=y

    #
    # Lock Debugging (spinlocks, mutexes, etc...)
    @@ -10696,7 +10694,6 @@
    # CONFIG_FUNCTION_PROFILER is not set
    CONFIG_STACK_TRACER=y
    # CONFIG_IRQSOFF_TRACER is not set
    -# CONFIG_PREEMPT_TRACER is not set
    # CONFIG_SCHED_TRACER is not set
    # CONFIG_HWLAT_TRACER is not set
    # CONFIG_OSNOISE_TRACER is not set
    \
     
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      Last update: 2023-10-20 15:38    [W:4.292 / U:0.028 seconds]
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