517f17aed0
Currently, jitter.sh assumes that the underlying hypervisor will be configured with all CPUs hotpluggable, with the possible exception of CPU 0. However, there are installations where the hypervisor prohibits offlining, which breaks jitter.sh. This commit therefore lists the CPUs that cannot be offlined up front, and checks for the case where no CPU can be offlined in the loop. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
97 lines
2.1 KiB
Bash
Executable File
97 lines
2.1 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 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=`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 $curcpu"
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fi
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done
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while :
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do
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# Check for done.
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t=`gawk -v s=$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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# 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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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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