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whitenoisedb
Asked: 2014-09-17 14:21:53 +0800 CST

CPU performance on sleep command

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This is rather a beginner question. I wonder what happens when sleep command is triggered from a bash script, for example. That job would still running, with less priority?

bash

1 Answers

  1. Best Answer

    Typically, sleep is the GNU sleep program. This program calls the GNU function xnanosleep, which in turn calls the Linux nanosleep system call. And:

    nanosleep()  suspends  the execution of the calling thread until either
at least the time specified in *req has elapsed, or the delivery  of  a
signal  that triggers the invocation of a handler in the calling thread
or that terminates the process.

    So the process is, by definition, not running (whatever maybe the priority), but suspended.

    Testing this out:

    sleep 10 & ps aux | grep $!
[1] 25682
muru  25682  0.0  0.0   7196   620 pts/13   SN   04:10   0:00 sleep 10

    The process state is SN:

       S    interruptible sleep (waiting for an event to complete)
   N    low-priority (nice to other users)

    Ignore the N, I'd guess that's how it was when it started out. So the effective state of sleep is interruptible sleep.

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