OpenStack Block Storage (Cinder)
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# Copyright (c) 2015 Hitachi Data Systems, Inc.
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""Volume copy throttling helpers."""
import contextlib
from oslo_concurrency import processutils
from oslo_log import log as logging
from cinder import exception
import cinder.privsep.cgroup
from cinder import utils
LOG = logging.getLogger(__name__)
class Throttle(object):
"""Base class for throttling disk I/O bandwidth"""
DEFAULT = None
@staticmethod
def set_default(throttle):
Throttle.DEFAULT = throttle
@staticmethod
def get_default():
return Throttle.DEFAULT or Throttle()
def __init__(self, prefix=None):
self.prefix = prefix or []
@contextlib.contextmanager
def subcommand(self, srcpath, dstpath):
"""Sub-command that reads from srcpath and writes to dstpath.
Throttle disk I/O bandwidth used by a sub-command, such as 'dd',
that reads from srcpath and writes to dstpath. The sub-command
must be executed with the generated prefix command.
"""
yield {'prefix': self.prefix}
class BlkioCgroup(Throttle):
"""Throttle disk I/O bandwidth using blkio cgroups."""
def __init__(self, bps_limit, cgroup_name):
self.bps_limit = bps_limit
self.cgroup = cgroup_name
self.srcdevs = {}
self.dstdevs = {}
try:
cinder.privsep.cgroup.cgroup_create(self.cgroup)
except processutils.ProcessExecutionError:
LOG.error('Failed to create blkio cgroup \'%(name)s\'.',
{'name': cgroup_name})
raise
def _get_device_number(self, path):
try:
return utils.get_blkdev_major_minor(path)
except exception.CinderException as e:
LOG.error('Failed to get device number for throttling: '
'%(error)s', {'error': e})
def _limit_bps(self, rw, dev, bps):
try:
cinder.privsep.cgroup.cgroup_limit(self.cgroup, rw, dev, bps)
except processutils.ProcessExecutionError:
LOG.warning('Failed to setup blkio cgroup to throttle the '
'device \'%(device)s\'.', {'device': dev})
def _set_limits(self, rw, devs):
total = sum(devs.values())
for dev in sorted(devs):
self._limit_bps(rw, dev, self.bps_limit * devs[dev] / total)
@utils.synchronized('BlkioCgroup')
def _inc_device(self, srcdev, dstdev):
if srcdev:
self.srcdevs[srcdev] = self.srcdevs.get(srcdev, 0) + 1
self._set_limits('read', self.srcdevs)
if dstdev:
self.dstdevs[dstdev] = self.dstdevs.get(dstdev, 0) + 1
self._set_limits('write', self.dstdevs)
@utils.synchronized('BlkioCgroup')
def _dec_device(self, srcdev, dstdev):
if srcdev:
self.srcdevs[srcdev] -= 1
if self.srcdevs[srcdev] == 0:
del self.srcdevs[srcdev]
self._set_limits('read', self.srcdevs)
if dstdev:
self.dstdevs[dstdev] -= 1
if self.dstdevs[dstdev] == 0:
del self.dstdevs[dstdev]
self._set_limits('write', self.dstdevs)
@contextlib.contextmanager
def subcommand(self, srcpath, dstpath):
srcdev = self._get_device_number(srcpath)
dstdev = self._get_device_number(dstpath)
if srcdev is None and dstdev is None:
yield {'prefix': []}
return
self._inc_device(srcdev, dstdev)
try:
yield {'prefix': ['cgexec', '-g', 'blkio:%s' % self.cgroup]}
finally:
self._dec_device(srcdev, dstdev)