44c1b48b31
This change adds a retry_if_busy decorator to the read_sys and write_sys functions in the filesystem module that will retry reads and writes up to 5 times with an linear backoff. This allows nova to tolerate short periods of time where sysfs retruns device busy. If the reties are exausted and offlineing a core fails a warning is log and the failure is ignored. onling a core is always treated as a hard error if retries are exausted. Closes-Bug: #2065927 Change-Id: I2a6a9f243cb403167620405e167a8dd2bbf3fa79
90 lines
2.8 KiB
Python
90 lines
2.8 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import os
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import typing as ty
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from oslo_log import log as logging
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from nova import exception
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from nova import filesystem
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import nova.privsep
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from nova.virt import hardware
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LOG = logging.getLogger(__name__)
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AVAILABLE_PATH = '/sys/devices/system/cpu/present'
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CPU_PATH_TEMPLATE = '/sys/devices/system/cpu/cpu%(core)s'
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def get_available_cores() -> ty.Set[int]:
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cores = filesystem.read_sys(AVAILABLE_PATH)
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return hardware.parse_cpu_spec(cores) if cores else set()
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def exists(core: int) -> bool:
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return core in get_available_cores()
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def gen_cpu_path(core: int) -> str:
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if not exists(core):
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LOG.warning('Unable to access CPU: %s', core)
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raise ValueError('CPU: %(core)s does not exist', core)
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return CPU_PATH_TEMPLATE % {'core': core}
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def get_online(core: int) -> bool:
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try:
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online = filesystem.read_sys(
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os.path.join(gen_cpu_path(core), 'online')).strip()
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except exception.FileNotFound:
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# The online file may not exist if we haven't written it yet.
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# By default, this means that the CPU is online.
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online = '1'
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return online == '1'
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@nova.privsep.sys_admin_pctxt.entrypoint
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def set_online(core: int) -> bool:
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# failure to online a core should be considered a failure
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# so we don't catch any exception here.
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filesystem.write_sys(os.path.join(gen_cpu_path(core), 'online'), data='1')
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return get_online(core)
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@nova.privsep.sys_admin_pctxt.entrypoint
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def set_offline(core: int) -> bool:
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try:
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filesystem.write_sys(os.path.join(
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gen_cpu_path(core), 'online'), data='0')
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except exception.DeviceBusy:
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# if nova is not able to offline a core it should not break anything
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# so we just log a warning and return False to indicate that the core
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# is not offline.
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LOG.warning('Unable to offline CPU: %s', core)
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return False
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return not get_online(core)
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def get_governor(core: int) -> str:
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return filesystem.read_sys(
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os.path.join(gen_cpu_path(core), 'cpufreq/scaling_governor')).strip()
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@nova.privsep.sys_admin_pctxt.entrypoint
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def set_governor(core: int, governor: str) -> str:
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filesystem.write_sys(
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os.path.join(gen_cpu_path(core), 'cpufreq/scaling_governor'),
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data=governor)
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return get_governor(core)
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