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Full Discussion: BASH Execution Delay / Speedup
Top Forums Shell Programming and Scripting BASH Execution Delay / Speedup Post 302933014 by Don Cragun on Tuesday 27th of January 2015 03:07:37 AM
Old 01-27-2015
So, from this code it seems that your intention is to simultaneously run an infinite number of jobs for every line in some file on your system. You do not care if any of these jobs start successfully. You do not care if any of these jobs complete successfully (or at all). You believe that you should be able to start an infinite number of jobs and all of those jobs should run as though they are the only job running on your system.

Unfortunately, I do not know of any system that will act anything at all like that. Nor, do I understand why you need an infinite loop to read lines in a file forever. Presumably your script terminates when the system kills it because it realizes you have exhausted system resources.

You say that a while read loop performs about the same way. You are correct in noting that an infinite loop is an infinite loop, but a while read loop would only have needed one process per line processed while your current nested loops use four processes per line processed plus 3 processes each time the file is processed. And, and a while read loop would read your file once each time you process the file while your current code reads the entire file n+1 times if your file contains n lines.

If, instead of processing a single file an infinite number of times, you want to process each line in a file once; and if instead of ignoring the success or failure of all of the jobs you start, you'd like to actually log any failures that might occur during processing and not terminate your script until all lines have been processed, tell us more about your system:
  1. Given the expected load on your system and the number of processors available to run your script, how many simultaneous processes should your script expect to be able to run?
  2. What does my_job do? (If it doesn't exit with a zero exit status if it completes successfully and exit with a non-zero exit status if it does not complete successfully, rewrite it so it does! If it exits before all children it has started have completed, rewrite it so it doesn't return until all of its children have finished!)
This User Gave Thanks to Don Cragun For This Post:
gmark99
 

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LEARN ABOUT DEBIAN

queuedefs

queuedefs(4)							   File Formats 						      queuedefs(4)

NAME

       queuedefs - queue description file for at, batch, and cron

SYNOPSIS

       /etc/cron.d/queuedefs

DESCRIPTION

       The queuedefs file describes the characteristics of the queues managed by cron(1M). Each non-comment line in this file describes one queue.
       The format of the lines are as follows:

	      q.[njobj][nicen][nwaitw]

       The fields in this line are:

       q	The name of the queue. a is the default queue for jobs started by at(1); b is the default queue for jobs  started  by  batch  (see
		at(1)); c is the default queue for jobs run from a crontab(1) file.

       njob	The  maximum  number of jobs that can be run simultaneously in that queue; if more than njob jobs are ready to run, only the first
		njob jobs will be run, and the others will be run as jobs that are currently running terminate.  The default value is  100.

       nice	The nice(1) value to give to all jobs in that queue that are not run with a user ID of super-user.  The default value is 2.

       nwait	The number of seconds to wait before rescheduling a job that was deferred because more than njob jobs were running in  that  job's
		queue, or because the system-wide limit of jobs executing has been reached.  The default value is 60.

       Lines beginning with # are comments, and are ignored.

EXAMPLES

       Example 1: A sample file.

       #
       #
       a.4j1n
       b.2j2n90w

       This  file  specifies that the a queue, for at jobs, can have up to 4 jobs running simultaneously; those jobs will be run with a nice value
       of 1.  As no nwait value was given, if a job cannot be run because too many other jobs are running cron will wait 60 seconds before  trying
       again to run it.

       The  b  queue, for batch(1) jobs, can have up to 2 jobs running simultaneously; those jobs will be run with a nice(1) value of 2.  If a job
       cannot be run because too many other jobs are running, cron(1M) will wait 90 seconds before trying again to run it. All	other  queues  can
       have up to 100 jobs running simultaneously; they will be run with a nice value of 2, and if a job cannot be run because too many other jobs
       are running cron will wait 60 seconds before trying again to run it.

FILES

       /etc/cron.d/queuedefs	       queue description file for  at, batch, and  cron.

SEE ALSO

       at(1), crontab(1), nice(1), cron(1M)

SunOS 5.10							    1 Mar 1994							      queuedefs(4)
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