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e95f6ccdbc
An embarrassing syntax error in jitter.sh makes for fixed spin time. This commit therefore makes it be variable, as intended, albeit with very coarse-grained adjustment. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
122 lines
2.8 KiB
Bash
Executable File
122 lines
2.8 KiB
Bash
Executable File
#!/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 jittering-path 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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# jittering-path: Path to file whose removal will stop this script.
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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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jittering=$2
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duration=$3
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sleepmax=${4-1000000}
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spinmax=${5-1000}
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n=1
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starttime=`gawk 'BEGIN { print systime(); }' < /dev/null`
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nohotplugcpus=
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for i in /sys/devices/system/cpu/cpu[0-9]*
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do
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if test -f $i/online
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then
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:
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else
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curcpu=`echo $i | sed -e 's/^[^0-9]*//'`
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nohotplugcpus="$nohotplugcpus $curcpu"
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fi
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done
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# Uses global variables startsecs, startns, endsecs, endns, and limit.
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# Exit code is success for time not yet elapsed and failure otherwise.
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function timecheck {
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local done=`awk -v limit=$limit \
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-v startsecs=$startsecs \
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-v startns=$startns \
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-v endsecs=$endsecs \
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-v endns=$endns < /dev/null '
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BEGIN {
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delta = (endsecs - startsecs) * 1000 * 1000;
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delta += int((endns - startns) / 1000);
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print delta >= limit;
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}'`
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return $done
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}
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while :
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do
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# Check for done.
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t=`gawk -v s=$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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# Check for stop request.
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if ! test -f "$jittering"
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then
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exit 1;
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fi
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# Set affinity to randomly selected online CPU
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if cpus=`grep 1 /sys/devices/system/cpu/*/online 2>&1 |
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sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
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then
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:
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else
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cpus=
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fi
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# Do not leave out non-hot-pluggable CPUs
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cpus="$cpus $nohotplugcpus"
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cpumask=`awk -v cpus="$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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print ca[int(rand() * ncpus + 1)];
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}' < /dev/null`
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n=$(($n+1))
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if ! taskset -c -p $cpumask $$ > /dev/null 2>&1
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then
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echo taskset failure: '"taskset -c -p ' $cpumask $$ '"'
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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, but with rather coarse granularity.
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limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
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srand(n + me + systime());
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printf("%06d", int(rand() * spinmax));
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}' < /dev/null`
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n=$(($n+1))
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startsecs=`date +%s`
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startns=`date +%N`
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endsecs=$startns
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endns=$endns
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while timecheck
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do
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endsecs=`date +%s`
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endns=`date +%N`
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done
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done
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exit 1
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