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    SubjectRe: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.32-15
    Date
    Here is my get_ltrace.sh script (at the end).

    So I read the preempt_max_latency (to see if its changed) before
    I copy the latency_trace output. I am not so sure that cat is
    really doing an "atomic" read when some of the latency traces
    are over 300 Kbytes in length.

    Also note that some of the files were empty :-(. I don't think
    I've seen that symptom before.

    Note that the preempt_max_latency value DID match the last line of
    the trace output in the example I described. It is just the header
    that had some stale data in it.

    --Mark

    --- get_ltrace.sh ---

    #!/bin/sh

    let MAX=`cat /proc/sys/kernel/preempt_max_latency`
    let I=0 J=1
    let MP=${1:-1000}
    echo "Current Maximum is $MAX, limit will be $MP."
    while (( I < 100 )) ; do
    sleep 1s
    let NOW=`cat /proc/sys/kernel/preempt_max_latency`
    if (( MAX != NOW )) ; then
    echo "New trace $I w/ $NOW usec latency."
    cat /proc/latency_trace > lt.`printf "%02d" $I`
    # sync ; sync
    let I++
    let MAX=NOW
    elif (( J++ >= 10 )) ; then
    if (( MAX != MP )) ; then
    echo "Resetting max latency from $MAX to $MP."
    echo $MP > /proc/sys/kernel/preempt_max_latency
    let MAX=$MP
    else
    echo "No new latency samples at `date`."
    fi
    let J=1
    # else do nothing...
    fi
    done

    -
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