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    SubjectRe: [patch] Real-Time Preemption, -RT-2.6.10-rc1-mm3-V0.7.23
    Ingo Molnar wrote:
    > i have released the -V0.7.23 Real-Time Preemption patch, which can be
    > downloaded from the usual place:
    >
    > http://redhat.com/~mingo/realtime-preempt/
    >

    I have found some test results that I find interesting with -V0.7.24. I
    modified the rtc-debug patch to work with any program that can use the
    rtc driver. It measures the latency between handling an interrupt and
    the actual read. The amlat program normally used with this patch sets up
    a signal handler that reads /dev/rtc when there is data available and
    then sleeps until it receives the signal. Realfeel just does a blocking
    read on /dev/rtc. Oh and both of them setup the rtc for periodic
    interrupts. I would probably expect the blocking read to be a bit faster
    but not dramatically. Here are the results of a couple of very short
    runs to illustrate the difference:

    amlat results (sleep/sighandler):
    Nov 10 21:10:39 daffy kernel: rtc histogram:
    Nov 10 21:10:39 daffy kernel: 26 1
    Nov 10 21:10:39 daffy kernel: 28 2152
    Nov 10 21:10:39 daffy kernel: 29 4286
    Nov 10 21:10:39 daffy kernel: 30 6857
    Nov 10 21:10:39 daffy kernel: 31 408
    Nov 10 21:10:39 daffy kernel: 32 9
    Nov 10 21:10:39 daffy kernel: 33 32
    Nov 10 21:10:39 daffy kernel: 34 217
    Nov 10 21:10:39 daffy kernel: 35 145
    Nov 10 21:10:39 daffy kernel: 36 26
    Nov 10 21:10:39 daffy kernel: 40 2
    Nov 10 21:10:39 daffy kernel: 41 9
    Nov 10 21:10:39 daffy kernel: 42 100
    Nov 10 21:10:39 daffy kernel: 43 180
    Nov 10 21:10:39 daffy kernel: 44 113
    Nov 10 21:10:39 daffy kernel: 45 30
    Nov 10 21:10:39 daffy kernel: 46 2
    Nov 10 21:10:39 daffy kernel: 47 4
    Nov 10 21:10:39 daffy kernel: 48 15
    Nov 10 21:10:39 daffy kernel: 49 4
    Nov 10 21:10:39 daffy kernel: 50 5
    Nov 10 21:10:39 daffy kernel:
    Nov 10 21:10:39 daffy kernel: Total samples: 14597

    realfeel results (blocking read):
    Nov 10 21:11:32 daffy kernel: rtc histogram:
    Nov 10 21:11:32 daffy kernel: 3 17844
    Nov 10 21:11:32 daffy kernel: 4 859
    Nov 10 21:11:32 daffy kernel: 5 34
    Nov 10 21:11:32 daffy kernel: 6 1
    Nov 10 21:11:32 daffy kernel: 8 1
    Nov 10 21:11:32 daffy kernel: 12 19
    Nov 10 21:11:32 daffy kernel: 13 41
    Nov 10 21:11:32 daffy kernel: 14 7
    Nov 10 21:11:32 daffy kernel:
    Nov 10 21:11:32 daffy kernel: Total samples: 18806

    Both of the above runs were with 'IRQ 8' running at SCHED_FF 99. Amlat
    and realfeel were both running at SCHED_FF 98. The updated rtc-debug
    patch to follow in case anyone is interested.

    kr
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