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

From: Daniel Walker (dwalker_at_mvista.com)
Date: 08/31/05

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    To: Steven Rostedt <rostedt@goodmis.org>
Date:	Wed, 31 Aug 2005 08:12:08 -0700

    There is already a suite HRT of tests they include a nanosleep jitter
    test with 8 or 9 other tests..

    find them inside the hrt-support patch at http://high-res-timer.sf.net

    Daniel

    On Wed, 2005-08-31 at 11:01 -0400, Steven Rostedt wrote:
    > 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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