02-13-2020
Another thought I've had is this.
If you can afford to you could stop cron from the command line and see if the spikes go away.
If you can't do that (because you need the cron scheduled processes to run regularly) but you know the footprint of the spike, you could briefly stop the cron process from the command line and then watch for a spike when you issue that cron start. It won't prove anything but does it look similar.
At boot time all crontabs are read into and held in memory and that is CPU intensive. Last modified times of crontabs are also cached. The periodical wake up checks the last modified times between disk and memory. So if you break the rules and modify a crontab directly, a new job you insert won't run at all until an integrity check by cron runs. So, so, so, I guess if you write a ditty to run every 2 seconds that you can monitor and manually insert it into root's crontab, does it start running at the next spike???
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cron(8) System Manager's Manual cron(8)
NAME
cron - The system clock daemon
SYNOPSIS
/usr/sbin/cron
DESCRIPTION
The cron daemon runs shell commands at specified dates and times. Commands that are to run according to a regular or periodic schedule are
found within the crontab files. Commands that are to run once only are found within the at files. You submit crontab and at file entries
by using the crontab and at commands. Because the cron process exits only when killed or when the system stops, only one cron daemon
should exist on the system at any given time. Normally, you start the cron daemon from within a run command file.
During process initialization and when cron detects a change, it examines the crontab and at files. This strategy reduces the overhead of
checking for new or changed files at regularly scheduled intervals. The cron command creates a log of its activities. The cron daemon
must be started from the system startup scripts because it must begin execution without a login user ID set. The cron daemon starts each
job with the following process attributes stored with the job by the invoking process: Login user ID Effective and real user IDs Effective
and real group IDs Supplementary groups
It also establishes the following attributes from the authentication profile of the account associated with the login user ID of the invok-
ing process: Audit control and disposition masks Kernel authorizations
DIAGNOSTICS
The at and batch programs will refuse to accept jobs submitted from processes whose login user ID is different from the real user ID.
FILES
Specifies the command path. Main cron directory Directory containing the crontab files. List of allowed users. List of denied users His-
tory information for cron Queue description file for at, batch, and cron
RELATED INFORMATION
Commands: at(1), crontab(1), rc0(8), rc2(8), rc3(8)
Files: queuedefs(4) delim off
cron(8)