[FYI] 2.6.13-rt3 and a nanosleep jitter test.

From: Steven Rostedt (rostedt_at_goodmis.org)
Date: 08/31/05

  • Next message: Hugh Dickins: "Re: [PATCH 1/1] Implement shared page tables" 
    To: Thomas Gleixner <tglx@linutronix.de>
Date:	Wed, 31 Aug 2005 11:01:54 -0400

    Thomas,

    I just was wondering how the HR Timers were in the latest -rtX patch and
    wrote my own little jitter test using nanosleep. Here's the results:

    On vanilla 2.6.13-rc7-git1 (Yes I need to get over to 2.6.13)

    # ./jitter
    starting calibrate
    finished calibrate: 2133.9060MHz 2133906034
    time slept: 0.010000000 sec: 0 nsec: 10000000
    max: 0.011997701
    min: 0.011890522
    avg: 0.011993485
    greatest time over: 1997.701 usecs
    never ran under (good!)
    average time over: 1993.485 usecs

    On 2.6.13-rt3:

    # ./jitter
    starting calibrate
    finished calibrate: 2133.2960MHz 2133295991
    time slept: 0.010000000 sec: 0 nsec: 10000000
    max: 0.010034857
    min: 0.010006309
    avg: 0.010009213
    greatest time over: 34.857 usecs
    never ran under (good!)
    average time over: 9.213 usecs

    Not bad. I then ran a clean kernel compile as root with a -j3 (this is
    an 2x SMP machine), and tried the test again.

    # ./jitter
    starting calibrate
    finished calibrate: 2133.3005MHz 2133300491
    time slept: 0.010000000 sec: 0 nsec: 10000000
    max: 0.010044836
    min: 0.010014244
    avg: 0.010030741
    greatest time over: 44.836 usecs
    never ran under (good!)
    average time over: 30.741 usecs

    Since the ticks per second is also calculated here, I ran it again using
    the calibration of the first run (still running that make):

    ./jitter -c 2133295991
    passed in calibrate: 2133.2960MHz 2133295991
    time slept: 0.010000000 sec: 0 nsec: 10000000
    max: 0.010051293
    min: 0.010012155
    avg: 0.010030237
    greatest time over: 51.293 usecs
    never ran under (good!)
    average time over: 30.237 usecs

    And once more using the calibration found by 2.6.13-rc7-git1 (still
    running that make):

    # ./jitter -c 2133906034
    passed in calibrate: 2133.9060MHz 2133906034
    time slept: 0.010000000 sec: 0 nsec: 10000000
    max: 0.010058339
    min: 0.010016418
    avg: 0.010025571
    greatest time over: 58.339 usecs
    never ran under (good!)
    average time over: 25.571 usecs

    Some info on my machine:

    $ cat /proc/cpuinfo
    processor : 0
    vendor_id : AuthenticAMD
    cpu family : 6
    model : 10
    model name : AMD Athlon(tm) MP 2800+
    stepping : 0
    cpu MHz : 2133.286
    cache size : 512 KB
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 1
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
    mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow
    bogomips : 4259.84

    processor : 1
    vendor_id : AuthenticAMD
    cpu family : 6
    model : 10
    model name : AMD Athlon(tm) Processor
    stepping : 0
    cpu MHz : 2133.286
    cache size : 512 KB
    fdiv_bug : no
    hlt_bug : no
    f00f_bug : no
    coma_bug : no
    fpu : yes
    fpu_exception : yes
    cpuid level : 1
    wp : yes
    flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge
    mca cmov pat pse36 mmx fxsr sse syscall mp mmxext 3dnowext 3dnow
    bogomips : 4259.84

    And attached is the jitter.c test. Must be run as root since it ups the
    priority to the max.

    Have fun,

    -- Steve

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  • Next message: Hugh Dickins: "Re: [PATCH 1/1] Implement shared page tables"