written by Radovan GarabĂk http://kassiopeia.juls.savba.sk/~garabik/software/polynice.html polynice is a nice(1)-like utility to throttle long running processes beyond what can be achieved by nice(1), by repeatedly suspending and resuming the process. It can also lower scheduler and I/O priorities, emulating nice(1) and ionice(1), and terminate the processes after given time, emulating timeout(1). Requirements ------------ polynice is written in python3 and runs mainly on Linux systems, but has been also tested on Mac OS X (Darwin). If psutil is installed, polynice will take advantage of it and children detection will be multiplatform. This will also enable nice(1) and ionice(1) functionality. If psutil is not installed, polynice will try to use nice(1) and ionice(1) to achieve the same functionality. There is some python2 compatibility, but not all functionality is guaranteed. Usage ----- You can use polynice either to run a command (in this case it mimics nice(1) usage), or to specify a PID of a running process. Throttling is done by periodically suspending (via SIGSTOP) and resuming (via SIGCONT) the process being throttled. The parameter -n A/B is used to specify the throttling ratio. The process will be suspended for A seconds, then it will run for B seconds, then again suspended for A seconds etc... Floating point values can be used, e.g. -n 0.4/2 will make the process run 2 seconds and suspend for 0.4 seconds out of 2.4 second time interval. If a single number is specified, B is taken to be 1, e.g. -n 3 will suspend the process for 3 seconds and run it 1 second. If 0 is used, do not throttle (useful in combination with -a or --term-after options). The default is 1/4, i.e. run the process 80% of the time, suspend it every 4th second for one second. Using the parameter --mode=random changes the semantics of throttling -- the process will be watched in B sized time interval, and for each of the intervals, it will be suspended with probability p=A/(A+B) (and run with probability 1-p). Statistically, the stop/run ratio will approximate the default (--mode=fixed) ratio if run sufficiently long. polynice is able to replace to a certain extent nice, renice and ionice commands. It accepts following compatibility options: -c IOCLASS, --class IOCLASS Sets process I/O scheduling class (the same as ionice): 0: none, 1: realtime, 2: best-effort, 3: idle. The same as the ionice parameter -c. --ion N, --classdata N Specifies the I/O scheduling class data. The same as the ionice parameter -n. --nn N Specifies the scheduling priority of the process. The same as the renice parameter -n. polynice can replace somewhat the timeout(1) command and accepts these options: --term-after DURATION If the controlled program is running after DURATION seconds, terminate it (with TERM signal). --kill-after DURATION Also send a KILL signal if the program is still running this long after the --term-after time expired and the TERM signal has been sent. Other options: --mode {random,fixed} Throttling mode. If fixed (the default), stop and re-run processes in fixed time intervals. If random, stop or run the processes with probability corresponding to the niceness. -a In addition to throttling, set maximum possible nice values (equivalent to ionice -c 3 nice -n 20) You can use the -v parameter to increase verbosity - print to stderr $ when process is stopped and = when run. Use -vv to be more verbose, print timestamp for each stop/run action to stderr. Use mostly with the -p option, otherwise it will clobber screen output. Use -vvv to be even more verbose. Useful for debugging. Caveats ------- polynice uses only pid's to identify processes, which can lead to a race condition - if the child's pid is reused in the time between creation of list of children and action (stopping or resuming), an incorrect process might be throttled (but at most for one control period). Examples -------- $ polynice -n 2/0.5 scp server:bigfile local/ will copy `bigfile' from the remote server, repeatedly suspending the scp command for 2 seconds, running it for 0.5 seconds, thus reducing the overall download speed to one fifths and keeping the network connection responsive. $ polynice -vv -n 3 -p 12345 will run the process (and all its children) with pid 12345 for 1 second, suspend it for 3 seconds, i.e. keeping CPU load to one fourth, thus reducing its power consumption and overheating. $ polynice program just use the default, run the program 80% of the time in 1 second intervals. $ polynice -a program will use the defaults as well, run the program 80% of the time in 1 second intervals, but in addition it will give it the lowest possible scheduler priority (equivalent to running `nice 20 program') and the lowest possible I/O priority (equivalent to running `ionice -c 3 program').