Top Forums UNIX for Advanced & Expert Users Nearly Random, Uncorrelated Server Load Average Spikes Post 303044059 by Neo on Thursday 13th of February 2020 05:36:48 AM
Quote:
Originally Posted by hicksd8
sar I agree is a good idea. Does the CPU spike coincide with an I/O spike??

In my experience this is likely to be kernel element feature. For example, are you watching the cron process itself because, as you will know, this wakes up periodically (and the regularity varies from kernel to kernel, somewhere between 4 and 24 hours) to integrity check its cron table cache in memory against the crontabs on disk. If there's a lot of cron jobs this process takes a short while.

So question is are you checking the cron process itself and not just cron jobs scheduled to run?

The above is a sheer guess.
Hi Dennis,

Quote:
Does the CPU spike coincide with an I/O spike??
No. I have mentioned this a number of times already, including the first post Smilie . There are no network I/O spikes.

Regarding disk I/O, I have not yet set up any instrumentation to attempt to correlate disk I/O to the spikes.
 
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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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