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I'm running a piece of OCR software [with gui, etc] on OSX that watches a folder and OCRs PDFs that are put in there. Occasionally the process starts behaving poorly and consumes a huge amount of system memory and CPU, running indefinitely on a particular PDF.

  • I'd like to know how to monitor that process to kill it under such circumstances.
  • I'd also like to prevent it from bringing the system to a halt, e.g. by sandboxing somehow.
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3 Answers

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Plain ol' ps can help with this: we run a process that considers the number of seconds of CPU each process has consumed according to ps versus the elapsed wallclock time and alerts a sysadmin to have a look if the ratio is excessive; you could of course tie that to a kill for specific processes if you so choose.

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Jeff - can you elaborate a touch. Which ps outputs are you using? What do you define as "excessive"? – Kyle Mar 21 '11 at 13:33
Well, the 'lstart' field will give you a proc's starting date and time in a parseable format, and the 'cputime' field will tell you the number of seconds of cpu time the process has consumed since it started. Convert current date/time and proc start date/time to epoch seconds, subtract to get the proc's total running seconds, then get the ratio of cpu seconds to running seconds. – Jeff Albert Mar 21 '11 at 16:38
What threshold is appropriate depends on your system and running processes; we alert by default when any process has used 300s of CPU time in 900s of wallclock, and then tune that figure based on a system's typical usage. – Jeff Albert Mar 21 '11 at 16:39
Thanks Jeff. Do you know of a way in which I can limit a process on OSX to consumption of only a certain amount of resources a priori? – Kyle Mar 23 '11 at 11:29
I don't know an easy way to specify a numeric value for cpu to wallclock time ratio; the 'nice' family of commands will allow you to specify a process's CPU scheduling priority, which might be what you're looking for (developer.apple.com/library/mac/#documentation/Darwin/Reference/…) – Jeff Albert Mar 23 '11 at 16:35
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to kill process you need to find its process number.

$ ps a| grep _process_name_

this results in list:

Sample:

$ ps a|grep Safari
31755 s000  R+     0:00.00 grep Safari

now kill the process:

kill 31755

There are some switches for kill command, sometimes you need to use kill -kill _process number_

To get a full list of options use main kill

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You can sandbox an application on OS X with the built in sandbox(7) facility. See the man pages for sandbox(7), sandbox-exec(1) and sandboxd(8). This repository of sandbox scripts may also be useful.

OS X 10.7 (Lion) will bring more application sandboxing features, as well, but the details on Apple's site are light. I would assume it will be related to the above feature.

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