83 lines
2.0 KiB
Bash
83 lines
2.0 KiB
Bash
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#!/bin/bash
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# SPDX-License-Identifier: GPL-2.0+
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#
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# Alternate sleeping and spinning on randomly selected CPUs. The purpose
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# of this script is to inflict random OS jitter on a concurrently running
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# test.
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#
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# Usage: jitter.sh me duration [ sleepmax [ spinmax ] ]
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#
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# me: Random-number-generator seed salt.
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# duration: Time to run in seconds.
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# sleepmax: Maximum microseconds to sleep, defaults to one second.
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# spinmax: Maximum microseconds to spin, defaults to one millisecond.
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#
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# Copyright (C) IBM Corporation, 2016
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#
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# Authors: Paul E. McKenney <paulmck@linux.ibm.com>
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me=$(($1 * 1000))
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duration=$2
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sleepmax=${3-1000000}
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spinmax=${4-1000}
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n=1
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starttime=`awk 'BEGIN { print systime(); }' < /dev/null`
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while :
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do
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# Check for done.
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t=`awk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
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if test "$t" -gt "$duration"
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then
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exit 0;
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fi
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# Set affinity to randomly selected online CPU
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cpus=`grep 1 /sys/devices/system/cpu/*/online |
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sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
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# Do not leave out poor old cpu0 which may not be hot-pluggable
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if [ ! -f "/sys/devices/system/cpu/cpu0/online" ]; then
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cpus="0 $cpus"
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fi
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cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
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srand(n + me + systime());
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ncpus = split(cpus, ca);
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curcpu = ca[int(rand() * ncpus + 1)];
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mask = lshift(1, curcpu);
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if (mask + 0 <= 0)
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mask = 1;
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printf("%#x\n", mask);
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}' < /dev/null`
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n=$(($n+1))
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if ! taskset -p $cpumask $$ > /dev/null 2>&1
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then
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echo taskset failure: '"taskset -p ' $cpumask $$ '"'
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exit 1
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fi
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# Sleep a random duration
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sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
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srand(n + me + systime());
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printf("%06d", int(rand() * sleepmax));
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}' < /dev/null`
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n=$(($n+1))
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sleep .$sleeptime
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# Spin a random duration
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limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
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srand(n + me + systime());
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printf("%06d", int(rand() * spinmax));
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}' < /dev/null`
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n=$(($n+1))
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for i in {1..$limit}
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do
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echo > /dev/null
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done
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done
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exit 1
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