Re: [Qemu-devel] [PATCH v5 5/5] qemu-iotests: Add 093 for IO throttling

[Max Reitz <mreitz@redhat.com>]

On 2015-01-26 at 22:03, Fam Zheng wrote:
> On Mon, 01/26 15:45, Max Reitz wrote:
>> On 2015-01-16 at 03:46, Fam Zheng wrote:
>>> This case utilizes qemu-io command "aio_{read,write} -q" to verify the
>>> effectiveness of IO throttling options.
>>>
>>> It's implemented by driving the vm timer from qtest protocol, so the
>>> throttling timers are signaled with determinied time duration. Then we
>>> verify the completed IO requests are within 10% error of bps and iops
>>> limits.
>>>
>>> "null" protocol is used as the disk backend so that no actual disk IO is
>>> performed on host, this will make the blockstats much more
>>> deterministic. Both "null-aio" and "null-co" are covered, which is also
>>> a simple cross validation test for the driver code.
>>>
>>> Signed-off-by: Fam Zheng <famz@redhat.com>
>>> ---
>>>   tests/qemu-iotests/093     | 103 +++++++++++++++++++++++++++++++++++++++++++++
>>>   tests/qemu-iotests/093.out |   5 +++
>>>   tests/qemu-iotests/group   |   1 +
>>>   3 files changed, 109 insertions(+)
>>>   create mode 100755 tests/qemu-iotests/093
>>>   create mode 100644 tests/qemu-iotests/093.out
>> NACK. This literally kills my laptop (I can recover when running this test
>> in tmpfs (for some reason inexplicable to me, since this uses the null block
>> drivers...), but I cannot when running it on my HDD).
>>
>> Would it be possible to use larger requests and smaller iops? (Or just the
>> same request size but smaller bps as well)
> Is it because of CPU or memory? 1000 requests for both read and write seem to
> be overkilling since we are measuring 1000 bps and 10 iops, please try if
> reducing to 100 requests works for you.

Probably memory, since I seem to recall you having the same model as me, 
but I can imagine you having more RAM...

100 requests do not work with 128,000 bps/64 iops/10 seconds (because 
that'd be more than 1 MB of data, whereas 100 requests of 4 kB are of 
course only 400 kB), but the following constellations work:
- 100 requests/128,000 bps/64 iops/1 second
- 100 requests/26,214 bps/8 iops/10 seconds (26,214 is about one tenth 
of 262,144 which is a multiple of 4,096, so the real value will not be 
too far off; the iops are limited by $number_of_requests / 
$duration_in_seconds)

I just hope there won't be some other poor guy for whom even this is too 
much...

Max

>> PS: Feel free to tell me I'm doing something wrong, of course. But just
>> ./check -T -raw -c writethrough 093 just killed my laptop, and simply
>> ./check -raw 093 would have probably killed it, too, if I wouldn't have held
>> down ^C after some seconds (I'm listening to music and that's when it began
>> stuttering...).
>>
>>> diff --git a/tests/qemu-iotests/093 b/tests/qemu-iotests/093
>>> new file mode 100755
>>> index 0000000..d12cc25
>>> --- /dev/null
>>> +++ b/tests/qemu-iotests/093
>>> @@ -0,0 +1,103 @@
>>> +#!/usr/bin/env python
>>> +#
>>> +# Tests for IO throttling
>>> +#
>>> +# Copyright (C) 2015 Red Hat, Inc.
>>> +#
>>> +# 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 2 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/>.
>>> +#
>>> +
>>> +import iotests
>>> +
>>> +class ThrottleTestCase(iotests.QMPTestCase):
>>> +    test_img = "null-aio://"
>>> +
>>> +    def blockstats(self, device):
>>> +        result = self.vm.qmp("query-blockstats")
>>> +        for r in result['return']:
>>> +            if r['device'] == device:
>>> +                stat = r['stats']
>>> +                return stat['rd_bytes'], stat['rd_operations'], stat['wr_bytes'], stat['wr_operations']
>>> +        raise Exception("Device not found for blockstats: %s" % device)
>>> +
>>> +    def setUp(self):
>>> +        self.vm = iotests.VM().add_drive(self.test_img)
>>> +        self.vm.launch()
>>> +
>>> +    def tearDown(self):
>>> +        self.vm.shutdown()
>>> +
>>> +    def do_test_throttle(self, seconds, params):
>>> +        def check_limit(limit, num):
>>> +            # IO throttling algorithm is discrete, allow 10% error so the test
>>> +            # is more
>> "more robust"?
> Yes :)
>
> Fam