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module/cpufreq: Add a contextmanager for temporary governor changes

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We may sometime want to temporarily use another governor, and then
restore whatever governor was used previously - for instance, RT-app
calibration ([1]) needs to use the performance governor, but we don't
want this to interfere with e.g. our current experiment.

[1]: https://github.com/ARM-software/lisa/blob/master/libs/wlgen/wlgen/rta.py#L118
This commit is contained in:
Valentin Schneider 2018-08-24 10:27:47 +01:00 committed by setrofim
parent 66be73be3e
commit 8cd1470bb8
1 changed files with 35 additions and 0 deletions
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35
devlib/module/cpufreq.py
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@ -12,6 +12,8 @@
# See the License for the specific language governing permissions and # See the License for the specific language governing permissions and
# limitations under the License. # limitations under the License.
# #
from contextlib import contextmanager
from devlib.module import Module from devlib.module import Module
from devlib.exception import TargetStableError from devlib.exception import TargetStableError
from devlib.utils.misc import memoized from devlib.utils.misc import memoized
@ -95,6 +97,39 @@ class CpufreqModule(Module):
self.target.write_value(sysfile, governor) self.target.write_value(sysfile, governor)
self.set_governor_tunables(cpu, governor, **kwargs) self.set_governor_tunables(cpu, governor, **kwargs)
@contextmanager
def use_governor(self, governor, cpus=None, **kwargs):
"""
Use a given governor, then restore previous governor(s)
:param governor: Governor to use on all targeted CPUs (see :meth:`set_governor`)
:type governor: str
:param cpus: CPUs affected by the governor change (all by default)
:type cpus: list
:Keyword Arguments: Governor tunables, See :meth:`set_governor_tunables`
"""
if not cpus:
cpus = range(self.target.number_of_cpus)
# Setting a governor & tunables for a cpu will set them for all cpus
# in the same clock domain, so only manipulating one cpu per domain
# is enough
domains = set(self.get_affected_cpus(cpu)[0] for cpu in cpus)
prev_governors = {cpu : (self.get_governor(cpu), self.get_governor_tunables(cpu))
for cpu in domains}
for cpu in domains:
self.set_governor(cpu, governor, **kwargs)
try:
yield
finally:
for cpu, (governor, tunables) in prev_governors.items():
self.set_governor(cpu, governor, **tunables)
def list_governor_tunables(self, cpu): def list_governor_tunables(self, cpu):
"""Returns a list of tunables available for the governor on the specified CPU.""" """Returns a list of tunables available for the governor on the specified CPU."""
if isinstance(cpu, int): if isinstance(cpu, int):