12.5 System Overloaded? Try Stopping Some Jobs

If your computer is barely crawling, you can kill (38.10 ) some processes... but you'll have to start them again later. On a Berkeley system, you can renice (39.11 ) the processes... but you won't be able to raise the priority again later, after the system speeds up, unless you're the superuser (1.24 ) .

If you don't need your results right away (and you won't get them, anyway, if the system is crawling!), try stopping some jobs. The best candidates are "CPU-eaters" like formatters (43.12 ) , compilers (52.8 ) , and any job that runs up a lot of time quickly in the ps (38.5 ) or time (39.2 ) reports. Start them again, later, and the jobs will take up where they left off.

If the job is in the foreground, just press CTRL-z (12.1 ) to stop it. If the job is running in the background and you're running csh or tcsh , use the shell's stop command with a job identifier - for example, stop %3 or stop %cc .

On other shells - even shells without job control (!) - you can use kill (38.10 ) with the -STOP signal and either the job number or process ID number. csh and tcsh have a stop command that does this for you. On other shells, if you'd like, you can add an alias named stop to the shell setup file (2.2 ) . Later, put the job back into the background with bg , or into the foreground with fg . For example:

bash$ alias stop='kill -STOP'


bash$ jobs


[1]+  Running                 g++ hugeprog.cc &
bash$ stop %1


[1]+  Stopped (signal)        g++ hugeprog.cc
    ...later...

bash$ bg %1


[1]+ g++ hugeprog.cc &