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???
This User Gave Thanks to hicksd8 For This Post:
10 More Discussions You Might Find Interesting
1. UNIX for Advanced & Expert Users
we have an unix system which has
load average normally about 20.
but while i am running a particular unix batch which performs heavy
operations on filesystem and database average load
reduces to 15.
how can we explain this situation?
while running that batch idle cpu time is about %60-65... (0 Replies)
Discussion started by: gfhgfnhhn
0 Replies
2. UNIX for Dummies Questions & Answers
Hello all, I have a question about load averages.
I've read the man pages for the uptime and w command for two or three different flavors of Unix (Red Hat, Tru64, Solaris). All of them agree that in the output of the 2 aforementioned commands, you are given the load average for the box, but... (3 Replies)
Discussion started by: Heathe_Kyle
3 Replies
3. UNIX for Dummies Questions & Answers
Hello, Here is the output of top command. My understanding here is,
the load average 0.03 in last 1 min, 0.02 is in last 5 min, 0.00 is in last 15 min.
By seeing this load average, When can we say that, the system load averge is too high?
When can we say that, load average is medium/low??... (8 Replies)
Discussion started by: govindts
8 Replies
4. Solaris
Hi,
i have installed solaris 10 on t-5120 sparc enterprise.
I am little surprised to see load average of 2 or around on this OS.
when checked with ps command following process is using highest CPU. looks like it is running for long time and does not want to stop, but I do not know... (5 Replies)
Discussion started by: upengan78
5 Replies
5. UNIX for Dummies Questions & Answers
Hello AlL,..
I want from experts to help me as my load average is increased and i dont know where is the problem !!
this is my top result :
root@a4s # top
top - 11:30:38 up 40 min, 1 user, load average: 3.06, 2.49, 4.66
Mem: 8168788k total, 2889596k used, 5279192k free, 47792k... (3 Replies)
Discussion started by: black-code
3 Replies
6. UNIX for Advanced & Expert Users
Hi ,
I am using 48 CPU sunOS server at my work.
The application has facility to check the current load average before starting a new process to control the load.
Right now it is configured as 48. So it does mean that each CPU can take maximum one proces and no processe is waiting.
... (2 Replies)
Discussion started by: kumaran_5555
2 Replies
7. Solaris
NPROC USERNAME SWAP RSS MEMORY TIME CPU
320 oracle 23G 22G 69% 582:55:11 85%
47 root 148M 101M 0.3% 99:29:40 0.3%
53 rafmsdb 38M 60M 0.2% 0:46:17 0.1%
1 smmsp 1296K 5440K 0.0% 0:00:08 0.0%
7 daemon ... (2 Replies)
Discussion started by: snjksh
2 Replies
8. UNIX for Dummies Questions & Answers
Hi,
I am getting a high load average, around 7, once an hour. It last for about 4 minutes and makes things fairly unusable for this time.
How do I find out what is using this. Looking at top the only thing running at the time is md5sum.
I have looked at the crontab and there is nothing... (10 Replies)
Discussion started by: sm9ai
10 Replies
9. UNIX for Dummies Questions & Answers
how load average is calculated and what exactly is it
difference between cpu% and load average (9 Replies)
Discussion started by: robo
9 Replies
10. Programming
Here we go....
Preface:
..... so in a galaxy far, far, far away from commercial, data sharing corporations.....
For this project, I used the ESP-WROOM-32 as an MQTT (publish / subscribe) client which receives Linux server "load averages" as messages published as MQTT pub/sub messages.... (6 Replies)
Discussion started by: Neo
6 Replies
CRON(8) BSD System Manager's Manual CRON(8)
NAME
cron -- daemon to execute scheduled commands (Vixie Cron)
SYNOPSIS
cron [-s] [-o] [-x debugflag[,...]]
DESCRIPTION
The cron utility is launched by launchd(8) when it sees the existence of /etc/crontab or files in /usr/lib/cron/tabs. There should be no
need to start it manually. See /System/Library/LaunchDaemons/com.vix.cron.plist for details.
The cron utility searches /usr/lib/cron/tabs for crontab files which are named after accounts in /etc/passwd; crontabs found are loaded into
memory. The cron utility also searches for /etc/crontab which is in a different format (see crontab(5)).
The cron utility then wakes up every minute, examining all stored crontabs, checking each command to see if it should be run in the current
minute. When executing commands, any output is mailed to the owner of the crontab (or to the user named in the MAILTO environment variable
in the crontab, if such exists).
Additionally, cron checks each minute to see if its spool directory's modification time (or the modification time on /etc/crontab) has
changed, and if it has, cron will then examine the modification time on all crontabs and reload those which have changed. Thus cron need not
be restarted whenever a crontab file is modified. Note that the crontab(1) command updates the modification time of the spool directory
whenever it changes a crontab.
Available options:
-s Enable special handling of situations when the GMT offset of the local timezone changes, such as the switches between the standard
time and daylight saving time.
The jobs run during the GMT offset changes time as intuitively expected. If a job falls into a time interval that disappears (for
example, during the switch from standard time) to daylight saving time or is duplicated (for example, during the reverse switch),
then it is handled in one of two ways:
The first case is for the jobs that run every at hour of a time interval overlapping with the disappearing or duplicated interval.
In other words, if the job had run within one hour before the GMT offset change (and cron was not restarted nor the crontab(5)
changed after that) or would run after the change at the next hour. They work as always, skip the skipped time or run in the added
time as usual.
The second case is for the jobs that run less frequently. They are executed exactly once, they are not skipped nor executed twice
(unless cron is restarted or the user's crontab(5) is changed during such a time interval). If an interval disappears due to the GMT
offset change, such jobs are executed at the same absolute point of time as they would be in the old time zone. For example, if
exactly one hour disappears, this point would be during the next hour at the first minute that is specified for them in crontab(5).
-o Disable the special handling of situations when the GMT offset of the local timezone changes, to be compatible with the old (default)
behavior. If both options -o and -s are specified, the option specified last wins.
-x debugflag[,...]
Enable writing of debugging information to standard output. One or more of the following comma separated debugflag identifiers must
be specified:
bit currently not used
ext make the other debug flags more verbose
load be verbose when loading crontab files
misc be verbose about miscellaneous one-off events
pars be verbose about parsing individual crontab lines
proc be verbose about the state of the process, including all of its offspring
sch be verbose when iterating through the scheduling algorithms
test trace through the execution, but do not perform any actions
FILES
/usr/lib/cron/tabs Directory for personal crontab files
SEE ALSO
crontab(1), launchctl(1), crontab(5), launchd.plist(5), launchd(8)
AUTHORS
Paul Vixie <paul@vix.com>
BSD
June 17, 2007 BSD