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    Subjectregression in TSC unstable?

    The ring-buffer-benchmark module creates a producer and consumer and loops
    on do_gettimeofday until it hits about 10 seconds. Then it calculates the
    number of events recorded / time running.

    After Ingo merged Linus's latest my tests when from 330ns per entry to
    880ns. After bisecting it I came down to this change:

    commit a71e4917dc0ebbcb5a0ecb7ca3486643c1c9a6e2
    Author: Len Brown <len.brown@intel.com>
    Date: Tue Apr 21 00:50:11 2009 -0400

    ACPI: idle: mark_tsc_unstable() at init-time, not run-time


    I've never had a problem with the TSC with this box before. It passes the
    synchronization phase, and until this commit, the TSC never was marked as
    unstable.

    Should it now be unstable? Or is this a false positive?

    # cat /proc/cpuinfo
    processor : 0
    vendor_id : GenuineIntel
    cpu family : 15
    model : 4
    model name : Intel(R) Xeon(TM) CPU 2.80GHz
    stepping : 1
    cpu MHz : 2793.272
    cache size : 1024 KB
    physical id : 0
    siblings : 2
    core id : 0
    cpu cores : 1
    apicid : 0
    initial apicid : 0
    fpu : yes
    fpu_exception : yes
    cpuid level : 5
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
    cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx
    lm constant_tsc pebs bts pni dtes64 monitor ds_cpl cid cx16 xtpr
    bogomips : 5586.54
    clflush size : 64
    cache_alignment : 128
    address sizes : 36 bits physical, 48 bits virtual
    power management:

    Anything else I might need to know?

    -- Steve



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