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Re: [PATCH blktests] loop/002: Regression testing for loop device flush

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  Re: [PATCH blktests] loop/002: Regression testing for loop device  flush Omar Sandoval <osandov@osandov.com> - 2017-06-26 21:00 +0200
    Re: [PATCH blktests] loop/002: Regression testing for loop device  flush James Wang <jnwang@suse.com> - 2017-06-27 03:40 +0200

#1675010 — Re: [PATCH blktests] loop/002: Regression testing for loop device flush

Hi, James, thanks for sending this in. Sorry for the delay, I've been
out of the office for a couple of weeks. A few comments below.

On Thu, Jun 08, 2017 at 08:28:12PM +0800, James Wang wrote:
> Add a regression testing for loop device. when an unbound device
> be close that take too long time. kernel will consume serveral orders
> of magnitude more wall time than it does for a mounted device.
> 
> Signed-off-by: James Wang <jnwang@suse.com>
> ---
>  tests/loop/002     | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  tests/loop/002.out |  2 ++
>  2 files changed, 79 insertions(+)
> 
> diff --git a/tests/loop/002 b/tests/loop/002
> new file mode 100755
> index 0000000..fd607d1
> --- /dev/null
> +++ b/tests/loop/002
> @@ -0,0 +1,77 @@
> +#!/bin/bash
> +#
> +# Test if close()ing a unbound loop device is too slow
> +# Copyright (C) 2017 James Wang
> +#
> +# This program is free software: you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation, either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +DESCRIPTION="Test if close()ing a unbound loop device is too slow"
> +
> +QUICK=1
> +
> +function run_test() {

For consistency with everything else in blktests, please don't use
"function" when defining a function.

> +	TIMEFORMAT='%5R'
> +	time {
> +		for f in `ls /dev/loop[0-9]*|sort`; do dd if=$f of=/dev/null  bs=512 count=1 >/dev/null 2>&1; done
> +	}
> +}
> +function clean_up() {
> +	if lsmod | grep loop >/dev/null 2>&1; then
> +		umount /dev/loop* >/dev/null 2>&1
> +		losetup -D
> +		sleep 5
> +		
> +		if ! rmmod loop;then
> +			return 2;
> +		fi
> +	fi
> +}
> +
> +function prepare() {
> +	modprobe loop max_loop=64

If loop is already loaded, this won't work, right?

> +	dd if=/dev/zero of=${TMPDIR}/disk bs=512 count=200K >/dev/null 2>&1
> +	for((i=0;i<4;i++))
> +	do
> +	        losetup -f ${TMPDIR}/disk;
> +	done
> +	mkfs.ext4 -F /dev/loop0 >/dev/null 2>&1

Hm, so if I happened to have something I care about on /dev/loop0,
running blktests will destroy it? This is a no-go.

> +	for((i=0;i<4;i++))
> +	do
> +	        mkdir -p t$i;
> +	        mount /dev/loop$i t$i;
> +	done
> +
> +}
> +
> +
> +test() {
> +	echo "Running ${TEST_NAME}"
> +
> +	prepare
> +	SECONDS=0
> +	run_test >/dev/null 2>&1
> +	DURATION=${SECONDS}

Nifty, I didn't know about $SECONDS.

> +
> +	clean_up
> +	if ! clean_up; then
> +		echo "Test complete"
> +		return 2
> +	fi
> +	echo "Test complete"
> +	if [[ "${DURATION}" -gt 1 ]]; then
> +		return 1
> +	else
> +		return 0
> +	fi

I'd really like a meaningful output if this test fails, so something
like this instead of the if/else

if [[ "${DURATION}" -gt 1 ]]; then
	echo "test took too long ($DURATION seconds)"
fi

> +}
> diff --git a/tests/loop/002.out b/tests/loop/002.out
> new file mode 100644
> index 0000000..5c34a37
> --- /dev/null
> +++ b/tests/loop/002.out
> @@ -0,0 +1,2 @@
> +Running loop/002
> +Test complete
> -- 
> 2.12.3
> 

Overall, is there an easier way to test this than setting up 64 loop
devices at modprobe time? E.g., can you losetup -f and run it on a
single loop device many times to measure the same issue?

Thanks again!

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#1675229

On 06/27/2017 02:58 AM, Omar Sandoval wrote:
> Hi, James, thanks for sending this in. Sorry for the delay, I've been
> out of the office for a couple of weeks. A few comments below.
>
> On Thu, Jun 08, 2017 at 08:28:12PM +0800, James Wang wrote:
>> Add a regression testing for loop device. when an unbound device
>> be close that take too long time. kernel will consume serveral orders
>> of magnitude more wall time than it does for a mounted device.
>>
>> Signed-off-by: James Wang <jnwang@suse.com>
>> ---
>>  tests/loop/002     | 77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  tests/loop/002.out |  2 ++
>>  2 files changed, 79 insertions(+)
>>
>> diff --git a/tests/loop/002 b/tests/loop/002
>> new file mode 100755
>> index 0000000..fd607d1
>> --- /dev/null
>> +++ b/tests/loop/002
>> @@ -0,0 +1,77 @@
>> +#!/bin/bash
>> +#
>> +# Test if close()ing a unbound loop device is too slow
>> +# Copyright (C) 2017 James Wang
>> +#
>> +# This program is free software: you can redistribute it and/or modify
>> +# it under the terms of the GNU General Public License as published by
>> +# the Free Software Foundation, either version 3 of the License, or
>> +# (at your option) any later version.
>> +#
>> +# This program is distributed in the hope that it will be useful,
>> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
>> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> +# GNU General Public License for more details.
>> +#
>> +# You should have received a copy of the GNU General Public License
>> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> +
>> +DESCRIPTION="Test if close()ing a unbound loop device is too slow"
>> +
>> +QUICK=1
>> +
>> +function run_test() {
> For consistency with everything else in blktests, please don't use
> "function" when defining a function.
I will fix it.
>> +	TIMEFORMAT='%5R'
>> +	time {
>> +		for f in `ls /dev/loop[0-9]*|sort`; do dd if=$f of=/dev/null  bs=512 count=1 >/dev/null 2>&1; done
>> +	}
>> +}
>> +function clean_up() {
>> +	if lsmod | grep loop >/dev/null 2>&1; then
>> +		umount /dev/loop* >/dev/null 2>&1
>> +		losetup -D
>> +		sleep 5
>> +		
>> +		if ! rmmod loop;then
>> +			return 2;
>> +		fi
>> +	fi
>> +}
>> +
>> +function prepare() {
>> +	modprobe loop max_loop=64
> If loop is already loaded, this won't work, right?
Actually, I could use clean_up() first , but due to My testing machine
has a bug causes clean_up() very slow......
I use call clean_up() before prepare(), make sense?
>
>> +	dd if=/dev/zero of=${TMPDIR}/disk bs=512 count=200K >/dev/null 2>&1
>> +	for((i=0;i<4;i++))
>> +	do
>> +	        losetup -f ${TMPDIR}/disk;
>> +	done
>> +	mkfs.ext4 -F /dev/loop0 >/dev/null 2>&1
> Hm, so if I happened to have something I care about on /dev/loop0,
> running blktests will destroy it? This is a no-go.
Yes, but due to our insert loop module and create a fake-disk and bound
to loop0, so format loop0 should doesn't matter.

>> +	for((i=0;i<4;i++))
>> +	do
>> +	        mkdir -p t$i;
>> +	        mount /dev/loop$i t$i;
>> +	done
>> +
>> +}
>> +
>> +
>> +test() {
>> +	echo "Running ${TEST_NAME}"
>> +
>> +	prepare
>> +	SECONDS=0
>> +	run_test >/dev/null 2>&1
>> +	DURATION=${SECONDS}
> Nifty, I didn't know about $SECONDS.
SECONDS is a built-in variable in bash, it will automatic increase.
>
>> +
>> +	clean_up
>> +	if ! clean_up; then
>> +		echo "Test complete"
>> +		return 2
>> +	fi
>> +	echo "Test complete"
>> +	if [[ "${DURATION}" -gt 1 ]]; then
>> +		return 1
>> +	else
>> +		return 0
>> +	fi
> I'd really like a meaningful output if this test fails, so something
> like this instead of the if/else
>
> if [[ "${DURATION}" -gt 1 ]]; then
> 	echo "test took too long ($DURATION seconds)"
> fi
I will fix this.
>> +}
>> diff --git a/tests/loop/002.out b/tests/loop/002.out
>> new file mode 100644
>> index 0000000..5c34a37
>> --- /dev/null
>> +++ b/tests/loop/002.out
>> @@ -0,0 +1,2 @@
>> +Running loop/002
>> +Test complete
>> -- 
>> 2.12.3
>>
> Overall, is there an easier way to test this than setting up 64 loop
> devices at modprobe time? E.g., can you losetup -f and run it on a
> single loop device many times to measure the same issue?
Use many loop devices for get a enough long time to compare with 1 second.
if we only create 1 loop device, I afraid it can't be measured.
In this scenario, I could get the duration of unbound and bound loop
device takes.
OK, I could try your suggestion.

I will send patch later.

James
>
> Thanks again!
>
>

-- 
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)

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