def set_tunable(self, disk, name, path, val):
"""
Given a disk name, a path to a tunable value under _TUNE_PATH and the
new value for the parameter, set the value and verify that the value
has been successfully set.
"""
fpath = partition.get_iosched_path(disk, path)
# Things might go wrong so we'll catch exceptions
try:
step = "open tunable path"
tunef = open(fpath, 'w', buffering=-1)
step = "write new tunable value"
tunef.write(val)
step = "close the tunable path"
tunef.close()
step = "read back new tunable value"
nval = open(fpath, 'r', buffering=-1).read().strip()
# For 'scheduler' we need to fish out the bracketed value
if name == "scheduler":
nval = re.match(".*\[(.*)\].*", nval).group(1)
except IOError as info:
# Special case: for some reason 'max_sectors_kb' often doesn't work
# with large values; try '128' if we haven't tried it already.
if name == "max_sectors_kb" and info.errno == 22 and val != '128':
self.set_tunable(disk, name, path, '128')
return
# Something went wrong, probably a 'config' problem of some kind
raise Exception("Unable to set tunable value '" + name +
"' at step '" + step + "': " + str(info))
except Exception:
# We should only ever see 'IOError' above, but just in case ...
raise Exception("Unable to set tunable value for " + name)
# Make sure the new value is what we expected
if nval != val:
raise Exception("Unable to correctly set tunable value for " +
name + ": desired " + val + ", but found " + nval)
return
def set_tunable(self, disk, name, path, val):
"""
Given a disk name, a path to a tunable value under _TUNE_PATH and the
new value for the parameter, set the value and verify that the value
has been successfully set.
"""
fpath = partition.get_iosched_path(disk, path)
# Things might go wrong so we'll catch exceptions
try:
step = "open tunable path"
tunef = open(fpath, 'w', buffering=-1)
step = "write new tunable value"
tunef.write(val)
step = "close the tunable path"
tunef.close()
step = "read back new tunable value"
nval = open(fpath, 'r', buffering=-1).read().strip()
# For 'scheduler' we need to fish out the bracketed value
if name == "scheduler":
nval = re.match(".*\[(.*)\].*", nval).group(1)
except IOError, info:
# Special case: for some reason 'max_sectors_kb' often doesn't work
# with large values; try '128' if we haven't tried it already.
if name == "max_sectors_kb" and info.errno == 22 and val != '128':
self.set_tunable(disk, name, path, '128')
return
# Something went wrong, probably a 'config' problem of some kind
raise Exception("Unable to set tunable value '" + name +
"' at step '" + step + "': " + str(info))