Re: [PATCH 1/1] generic: fsstress with cpu offlining

["Darrick J. Wong" <djwong@kernel.org>]

On Sat, Sep 18, 2021 at 12:04:49AM +0530, riteshh wrote:
> On 21/09/15 04:42PM, Darrick J. Wong wrote:
> > From: Darrick J. Wong <djwong@kernel.org>
> >
> > Exercise filesystem operations when we're taking CPUs online and offline
> > throughout the test.
> 
> Nice test coverage. Btw, I may have missed older versions, but could you point
> to the link which points to the bugs which this test uncovered?
> I guess it will be good to add tha in the comment section of test description
> too.

I didn't uncover any bugs with 5.14, fortunately.  Dave Chinner was
messing around with per-CPU lists in XFS, so I figured I had better
write something to exercise the cpu-dead handlers to try to make sure
there weren't any obvious bugs in the code, and this is the result.

> This also made me think whether doing memory online/offline while
> running
> fsstress, makes any sense?

Heh, perhaps.  I hadn't gotten /that/ far... :)

--D

> 
> >
> > Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> > ---
> >  tests/generic/726     |   74 +++++++++++++++++++++++++++++++++++++++++++++++++
> >  tests/generic/726.out |    2 +
> >  2 files changed, 76 insertions(+)
> >  create mode 100755 tests/generic/726
> >  create mode 100644 tests/generic/726.out
> >
> >
> > diff --git a/tests/generic/726 b/tests/generic/726
> > new file mode 100755
> > index 00000000..1a3f2fad
> > --- /dev/null
> > +++ b/tests/generic/726
> > @@ -0,0 +1,74 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0
> > +# Copyright (c) 2021 Oracle, Inc.  All Rights Reserved.
> > +#
> > +# FS QA Test No. 726
> > +#
> > +# Run an all-writes fsstress run with multiple threads while exercising CPU
> > +# hotplugging to shake out bugs in the write path.
> > +#
> > +. ./common/preamble
> > +_begin_fstest auto rw stress
> 
> Does it qualify for auto? This definitely is taking a longer time compared to
> other auto tests on my qemu setup.
> 
> > +
> > +# Override the default cleanup function.
> > +_cleanup()
> > +{
> > +	cd /
> > +	rm -f $tmp.*
> > +	$KILLALL_PROG -9 fsstress > /dev/null 2>&1
> > +	wait	# for exercise_cpu_hotplug subprocess
> > +	for i in "$sysfs_cpu_dir/"cpu*/online; do
> > +		echo 1 > "$i" 2>/dev/null
> > +	done
> > +	test -n "$stress_dir" && rm -r -f "$stress_dir"
> > +}
> > +
> > +exercise_cpu_hotplug()
> > +{
> > +	while [ -e $sentinel_file ]; do
> > +		local idx=$(( RANDOM % nr_hotplug_cpus ))
> > +		local cpu="${hotplug_cpus[idx]}"
> > +		local action=$(( RANDOM % 2 ))
> > +
> > +		echo "$action" > "$sysfs_cpu_dir/cpu$cpu/online" 2>/dev/null
> > +		sleep 0.5
> > +	done
> > +}
> > +
> > +_supported_fs generic
> > +_require_test
> > +_require_command "$KILLALL_PROG" "killall"
> > +
> > +sysfs_cpu_dir="/sys/devices/system/cpu"
> > +
> > +# Figure out which CPU(s) support hotplug.
> > +nrcpus=$(getconf _NPROCESSORS_CONF)
> > +hotplug_cpus=()
> > +for ((i = 0; i < nrcpus; i++ )); do
> > +	test -e "$sysfs_cpu_dir/cpu$i/online" && hotplug_cpus+=("$i")
> > +done
> > +nr_hotplug_cpus="${#hotplug_cpus[@]}"
> > +test "$nr_hotplug_cpus" -gt 0 || _notrun "CPU hotplugging not supported"
> > +
> > +stress_dir="$TEST_DIR/$seq"
> > +rm -r -f "$stress_dir"
> > +mkdir -p "$stress_dir"
> > +
> > +echo "Silence is golden."
> > +
> > +sentinel_file=$tmp.hotplug
> > +touch $sentinel_file
> > +exercise_cpu_hotplug &
> > +
> > +# Cap the number of fsstress threads at one per hotpluggable CPU if we exceed
> > +# 1024 IO threads, per maintainer request.
> > +nr_cpus=$((LOAD_FACTOR * nr_hotplug_cpus))
> > +test "$nr_cpus" -gt 1024 && nr_cpus="$nr_hotplug_cpus"
> > +
> > +nr_ops=$((25000 * TIME_FACTOR))
> > +$FSSTRESS_PROG $FSSTRESS_AVOID -w -d $stress_dir -n $nr_ops -p $nr_cpus >> $seqres.full
> > +rm -f $sentinel_file
> > +
> > +# success, all done
> > +status=0
> > +exit
> > diff --git a/tests/generic/726.out b/tests/generic/726.out
> > new file mode 100644
> > index 00000000..6839f8ce
> > --- /dev/null
> > +++ b/tests/generic/726.out
> > @@ -0,0 +1,2 @@
> > +QA output created by 726
> > +Silence is golden.
> >