Erich Schreiber wrote: > In the Python Library Reference the explanation of the time.sleep() > function reads amongst others: > > >>The actual suspension time may be less than that requested because >>any caught signal will terminate the sleep() following execution >>of that signal's catching routine. Also, the suspension time may >>be longer than requested by an arbitrary amount because of the >>scheduling of other activity in the system. > > > I don't understand the first part of this passage with the premature > wakeup. What signals would that be?
That would be signals from the OS, frinstance, if you type ^C into the python console, or kill the process from another command line. > I've written a script that tries to bench the responsiveness of a > virtual Linux server. My script sleeps for a random time and on waking > up calculates the difference of the proposed and actual wakeup time. > > The essential code fragment is > > while True: > ts = tDelay() > t1 = time.time() > time.sleep(ts) > t2 = time.time() > twu = str(datetime.datetime.utcfromtimestamp(t1 + ts)) > logResults(LOGFILE, twu, ts, int((t2-t1-ts)*1000)) > > Whereas tDelay() returns a (logarithmically) randomly distributed real > number in the range [0.01, 1200] which causes the process to sleep > from 10 ms to 20 minutes. > > In the logs I see a about 1% of the wake-up delays beeing negative > from -1ms to about -20ms somewhat correlated with the duration of the > sleep. 20 minute sleeps tend to wake-up earlier then sub-second > sleeps. Can somebody explain this to me? > I think the sleep times are quantised to the granularity of the system clock, shich varies from os to os. From memory, windows 95 has a 55mS timer, NT is less (19mS?), Linux and solaris 1mS. All this is from memory, and really comes from discussions I have seen about sleep and time in java, but I am guessing that there are similarities. Steve -- http://mail.python.org/mailman/listinfo/python-list
