RE: Re: Isolation and time

["Dan Magenheimer" <dan.magenheimer@oracle.com>]

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> Yes, I reckon that could work pretty well.
> 
>  -- Keir

I'm pretty sure the attached script when run in
domain0 will generate an appropriately random CPU
load on every domain0 vcpu.  For each vcpu, it
randomly eats CPU for a fraction of a second, then
sleeps for the same amount of time, then repeats.
Thus any timer-under-test domain should see
random unscheduled intervals which hopefully
occur at random fractions of its timer tick.

I'll probably use this for future timer testing,
so let me know if you see problems with this
approach.

Thanks,
Dan

P.S. May be dependent on RH-based dom0.

> -----Original Message-----
> From: Keir Fraser [mailto:keir.fraser@eu.citrix.com]
> Sent: Saturday, June 14, 2008 9:25 AM
> 
> <dan.magenheimer@oracle.com> wrote:
> 
> > That's what I thought.  Sorry to belabour, but
> > that leads to one more question:
> >
> > If one were to put an appropriately random CPU-only load
> > on every processor on domain0 (assuming domain0 runs
> > on all physical processors), then this would presumably
> > be sufficient to exercise a domain-under-test's time
> > synchronization, correct?
> 
> Yes, I reckon that could work pretty well.
> 
>  -- Keir

[-- Attachment #2: dom0busy.sh --]
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#!/bin/bash
# dom0busy - randomly busies all dom0 vcpus
# keeps cpu busy for a fraction of a second, then sleeps for the same; repeat
# run in domain0 as root, can be monitored in top
TMPFILE=`mktemp /tmp/dom0busy.XXX` || exit 1
(
cat <<'EOF'
#!/bin/bash
while true; do
	RANDOM=$$$(date +%S)
	r1=$RANDOM
	r2=$RANDOM
	let loops="($r1*$r2)%10000"
	start=`date +%s.%N`
	while [ $loops -gt 0 ]; do
		let loops="$loops-1"
	done
	fin=`date +%s.%N`
	elapsed=`echo "scale=3; $fin - $start" | bc -iq`
	#echo sleeping for $elapsed sec
	/bin/sleep $elapsed
done &
EOF
) > $TMPFILE
chmod +x $TMPFILE
ncpus=`xm list | grep Domain-0 | sed 's/  */ /g' | cut -f4 -d" "`
echo Busying $ncpus cpus
let ncpus="$ncpus-1"
while [ $ncpus -ge 0 ]; do
	echo busying cpu $ncpus
	taskset -c $ncpus $TMPFILE
	let ncpus="$ncpus-1"
done
/bin/rm -rf $TMPFILE


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