I have to display the CPU usage on my application and update it in real time. I am using top command to get the CPU usage i.e.
I add the two highlighted values to get the CPU usage. The command which i am using to add the highlighted values and get the final CPU usage is:
top -b -n 2 | grep Cpu | awk '{printf "CPU Load:%.2f\n", $(NF-13) + $(NF-15)}' | sed -n '2 p'
Issues is that, this command stops working after sometime i.e. for 3-4 minutes i do get the CPU usage but after that command does not process and i do not get the updated value. I am running this command in a loop.
Any help would be much appreciated.
I am using the similar script without issues for some time now:
top -bn2 | grep Cpu | tail -n1 | sed -e 's/.*, *\([0-9.]*\)%* id.*/\1/' | awk '{print 100-$1}'
The script takes the 'idle' time from top output and deduct it from 100% to get cpu usage.
The periodicity of the loop in which you are calling the script should not be faster than the time needed for the script to finish. Otherwise, you may get multiple 'top's running in parallel. This primarily depends on the 'top' default delay on your system, on mine, it is about 5s, but you can set this with -d switch.
I'm pretty inexperienced with Linux bash. That being said, I have a CentOS7 machine that runs a COTS application server. This application server runs other processes that sometimes hang. Since I have no control over the start of these processes, I'm looking for a script that runs every 2 minutes that kills processes of the name "spicer" that have been running for longer than 10 minutes. I've looked around and have only been able to find answers for processes that are run and owned by me.
I use the command ps -eo pid, command,etime | grep spicer to get all the spicer processes. The output of this command looks like:
18216 spicer -l/opt/otmm-10.5/Spi 14:20
18415 spicer -l/opt/otmm-10.5/Spi 11:49
etc...
18588 grep --color=auto spicer
I don't know if there's a way to parse this directly in bash. I'm also not well-versed at all in other Linux tools. I know that awk (or gawk) could possibly help.
EDIT
I have no control over the data that the process is working on.
What about wrapping the executable of spicer and start it using the timeout command? Let's say it is installed in /usr/bin/spicer. Then issue:
cp /usr/bin/spicer{,.orig}
echo '#!/bin/bash' > /usr/bin/spicer
echo 'timeout 10m spicer.orig "$#"' >> /usr/bin/spicer
Another approach would be to create a cronjob defintion into /etc/cron.d/kill_spicer. Like this:
* * * * * root kill $(ps --no-headers -C spicer -o pid,etimes | awk '$2>=600{print $1}')
The cronjob will get executed minutely and uses ps to obtain a list of spicer processes that run longer than 10minutes and passes them to kill.
Probably you even want kill -9 if the process is hanging.
You can use the -C option of ps to select processes by name.
ps --no-headers -C spicer -o pid,etime
Then you can use cut to filter the results, if the spacing is consistent. On my system the pid field takes up 8 characters, so I'd use
kill $(ps --no-headers -C spicer -o pid,etime | cut -c-8)
If the spacing is inconsistent (but if so, what kind of messed up ps are you using? :-P), you can use awk { print $1 } instead of cut.
I try to get the output of the top 5 processes in a Linux system. I'm expecting to get the percentage of processor (CPU) used but I'm a little worried about if the command that I'm using gets the CPU or the RAM; what is the output?
ps -A --sort -rss -o comm,pmem | head -n 6
The man documentation of ps indicates that the output is the process, but I'm suspecting that is the RAM memory. Could you clarify the output for me, please?
It's a process sorting by rss which is resident set size - memory usage - and then showing you the command and percentage memory usage. Header line and top 5 processes.
For an explanation of what RSS actually is, see this answer on unix: https://unix.stackexchange.com/questions/35129/need-explanation-on-resident-set-size-virtual-size
To get the top 5 by CPU load as you asked:
ps -A --sort -pcpu -o comm,pmem,pcpu | head -n 6
I would like to monitor the number of threads used by a specific process on Linux.
Is there an easy way to get this information without impacting the performance of the process?
try
ps huH p <PID_OF_U_PROCESS> | wc -l
or htop
To get the number of threads for a given pid:
$ ps -o nlwp <pid>
Where nlwp stands for Number of Light Weight Processes (threads). Thus ps aliases nlwp to thcount, which means that
$ ps -o thcount <pid>
does also work.
If you want to monitor the thread count, simply use watch:
$ watch ps -o thcount <pid>
To get the sum of all threads running in the system:
$ ps -eo nlwp | tail -n +2 | awk '{ num_threads += $1 } END { print num_threads }'
Each thread in a process creates a directory under /proc/<pid>/task. Count the number of directories, and you have the number of threads.
cat /proc/<PROCESS_PID>/status | grep Threads
ps -eLf on the shell shall give you a list of all the threads and processes currently running on the system.
Or, you can run top command then hit 'H' to toggle thread listings.
$ ps H p pid-id
H - Lists all the individual threads in a process
or
$cat /proc/pid-id/status
pid-id is the Process ID
eg.. (Truncated the below output)
root#abc:~# cat /proc/8443/status
Name: abcdd
State: S (sleeping)
Tgid: 8443
VmSwap: 0 kB
Threads: 4
SigQ: 0/256556
SigPnd: 0000000000000000
If you use:
ps uH p <PID_OF_U_PROCESS> | wc -l
You have to subtract 1 to the result, as one of the lines "wc" is counting is the headers of the "ps" command.
My answer is more gui, but still within terminal. Htop may be used with a bit of setup.
Start htop.
Enter setup menu by pressing F2.
From leftmost column choose "Columns"
From rightmost column choose the column to be added to main monitoring output, "NLWP" is what you are looking for.
Press F10.
JStack is quite inexpensive - one option would be to pipe the output through grep to find active threads and then pipe through wc -l.
More graphically is JConsole, which displays the thread count for a given process.
Here is one command that displays the number of threads of a given process :
ps -L -o pid= -p <pid> | wc -l
Unlike the other ps based answers, there is here no need to substract 1 from its output as there is no ps header line thanks to the -o pid=option.
Newer JDK distributions ship with JConsole and VisualVM. Both are fantastic tools for getting the dirty details from a running Java process. If you have to do this programmatically, investigate JMX.
If you're looking for thread count for multiple processes, the other answers won't work well for you, since you won't see the process names or PIDs, which makes them rather useless. Use this instead:
ps -o pid,nlwp,args -p <pid_1> <pid_2> ... <pid_N>
In order to watch the changes live, just add watch:
watch ps -o pid,nlwp,args -p <pid_1> <pid_2> ... <pid_N>
jvmtop can show the current jvm thread count beside other metrics.
The easiest way is using "htop". You can install "htop" (a fancier version of top) which will show you all your cores, process and memory usage.
Press "Shift+H" to show all process or press again to hide it.
Press "F4" key to search your process name.
Installing on Ubuntu or Debian:
sudo apt-get install htop
Installing on Redhat or CentOS:
yum install htop
dnf install htop [On Fedora 22+ releases]
If you want to compile "htop" from source code, you will find it here.
If you are trying to find out the number of threads using cpu for a given pid I would use:
top -bc -H -n2 -p <pid> | awk '{if ($9 != "0.0" && $1 ~ /^[0-9]+$/) print $1 }' | sort -u | wc -l
If you want the number of threads per user in a linux system then you should use:
ps -eLf | grep <USER> | awk '{ num += $6 } END { print num }'
where as <USER> use the desired user name.
If you're interested in those threads which are really active -- as in doing something (not blocked, not timed_waiting, not reporting "thread running" but really waiting for a stream to give data) as opposed to sitting around idle but live -- then you might be interested in jstack-active.
This simple bash script runs jstack then filters out all the threads which by heuristics seem to be idling, showing you stack traces for those threads which are actually consuming CPU cycles.
First get the process ID (pid) by executing below command:
ps -ef | grep (for e.g ps -ef | grep java)
Now replace the pid in below command and execute to get the total thread count of a process.
ps huH p | wc -l
VisualVM can show clear states of threads of a given JVM process
I have the following problem: some processes, generated dynamically, have a tendency to eat 100% of CPU. I would like to limit all the process matching some criterion (e.g. process name) to a certain amount of CPU percentage.
The specific problem I'm trying to solve is harnessing folding#home worker processes. The best solution I could think of is a perl script that's executed periodically and uses the cpulimit utility to limit the processes (if you're interested in more details, check this blog post). It works, but it's a hack :/
Any ideas? I would like to leave the handling of processes to the OS :)
Thanks again for the suggestions, but we're still missing the point :)
The "slowDown" solution is essentially what the "cpulimit" utility does. I still have to take care about what processes to slow down, kill the "slowDown" process once the worker process is finished and start new ones for new worker processes. It's precisely what I did with the Perl script and a cron job.
The main problem is that I don't know beforehand what processes to limit. They are generated dynamically.
Maybe there's a way to limit all the processes of one user to a certain amount of CPU percentage? I already set up a user for executing the folding#home jobs, hoping that i could limit him with the /etc/security/limits.conf file. But the nearest I could get there is the total CPU time per user...
It would be cool if to have something that enables you to say:
"The sum of all CPU % usage of this user's processes cannot exceed 50%". And then let the processes fight for that 50% of CPU regarding to their priorities...
Guys, thanks for your suggestions, but it's not about priorities - I want to limit the CPU % even when there's plenty of CPU time available. The processes are already low priority, so they don't cause any performance issues.
I would just like to prevent the CPU from running on 100% for extended periods...
I had a slightly similar issue with gzip.
Assuming we want to decrease the CPU of a gzip process:
gzip backup.tar & sleep 2 & cpulimit --limit 10 -e gzip -z
Options:
I found sleep useful as the cpulimit sometimes didn't pick up the new gzip process immediately
--limit 10 limits gzip CPU usage to 10%
-z automatically closes cpulimit when gzip process finishes
Another option is to run the cpulimit daemon.
I don't remember and dont think there was something like this in the unix scheduler. You need a little program which controls the other process and does the following:
loop
wait for some time tR
send SIGSTOP to the process you want to be scheduled
wait for some time tP
send SIGCONT to the process.
loopEnd
the ratio tR/tP controls the cpu load.
Here is a little proof of concept. "busy" is the program which uses up your cpu time and which you want to be slowed-down by "slowDown":
> cat > busy.c:
main() { while (1) {}; }
> cc -o busy busy.c
> busy &
> top
Tasks: 192 total, 3 running, 189 sleeping, 0 stopped, 0 zombie
Cpu(s): 76.9% us, 6.6% sy, 0.0% ni, 11.9% id, 4.5% wa, 0.0% hi, 0.0% si
Mem: 6139696k total, 6114488k used, 25208k free, 115760k buffers
Swap: 9765368k total, 1606096k used, 8159272k free, 2620712k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
26539 cg 25 0 2416 292 220 R 90.0 0.0 3:25.79 busy
...
> cat > slowDown
while true; do
kill -s SIGSTOP $1
sleep 0.1
kill -s SIGCONT $1
sleep 0.1
done
> chmod +x slowDown
> slowDown 26539 &
> top
Tasks: 200 total, 4 running, 192 sleeping, 4 stopped, 0 zombie
Cpu(s): 48.5% us, 19.4% sy, 0.0% ni, 20.2% id, 9.8% wa, 0.2% hi, 2.0% si
Mem: 6139696k total, 6115376k used, 24320k free, 96676k buffers
Swap: 9765368k total, 1606096k used, 8159272k free, 2639796k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
26539 cg 16 0 2416 292 220 T 49.7 0.0 6:00.98 busy
...
ok, that script needs some more work (for example, to care for being INTR-upted and let the controlled process continue in case it was stopped at that moment), but you get the point. I would also write that little script in C or similar and compute the cpu ratio from a comand line argument....
regards
I think in Linux there is no solution to cap the cpu usage, but there is an acceptable way to limit any process to a certain CPU usage: http://ubuntuforums.org/showthread.php?t=992706
In case they remove the info, here is again
INSTALL PACKAGES
Install cpulimit package.
Code:
sudo apt-get install cpulimit
Install gawk package.
Code:
sudo apt-get install gawk
CREATE CPULIMIT DAEMON FILE
Open text editor with root privileges and save bellow daemon script text to new file /usr/bin/cpulimit_daemon.sh
Code:
#!/bin/bash
# ==============================================================
# CPU limit daemon - set PID's max. percentage CPU consumptions
# ==============================================================
# Variables
CPU_LIMIT=20 # Maximum percentage CPU consumption by each PID
DAEMON_INTERVAL=3 # Daemon check interval in seconds
BLACK_PROCESSES_LIST= # Limit only processes defined in this variable. If variable is empty (default) all violating processes are limited.
WHITE_PROCESSES_LIST= # Limit all processes except processes defined in this variable. If variable is empty (default) all violating processes are limited.
# Check if one of the variables BLACK_PROCESSES_LIST or WHITE_PROCESSES_LIST is defined.
if [[ -n "$BLACK_PROCESSES_LIST" && -n "$WHITE_PROCESSES_LIST" ]] ; then # If both variables are defined then error is produced.
echo "At least one or both of the variables BLACK_PROCESSES_LIST or WHITE_PROCESSES_LIST must be empty."
exit 1
elif [[ -n "$BLACK_PROCESSES_LIST" ]] ; then # If this variable is non-empty then set NEW_PIDS_COMMAND variable to bellow command
NEW_PIDS_COMMAND="top -b -n1 -c | grep -E '$BLACK_PROCESSES_LIST' | gawk '\$9>CPU_LIMIT {print \$1}' CPU_LIMIT=$CPU_LIMIT"
elif [[ -n "$WHITE_PROCESSES_LIST" ]] ; then # If this variable is non-empty then set NEW_PIDS_COMMAND variable to bellow command
NEW_PIDS_COMMAND="top -b -n1 -c | gawk 'NR>6' | grep -E -v '$WHITE_PROCESSES_LIST' | gawk '\$9>CPU_LIMIT {print \$1}' CPU_LIMIT=$CPU_LIMIT"
else
NEW_PIDS_COMMAND="top -b -n1 -c | gawk 'NR>6 && \$9>CPU_LIMIT {print \$1}' CPU_LIMIT=$CPU_LIMIT"
fi
# Search and limit violating PIDs
while sleep $DAEMON_INTERVAL
do
NEW_PIDS=$(eval "$NEW_PIDS_COMMAND") # Violating PIDs
LIMITED_PIDS=$(ps -eo args | gawk '$1=="cpulimit" {print $3}') # Already limited PIDs
QUEUE_PIDS=$(comm -23 <(echo "$NEW_PIDS" | sort -u) <(echo "$LIMITED_PIDS" | sort -u) | grep -v '^$') # PIDs in queue
for i in $QUEUE_PIDS
do
cpulimit -p $i -l $CPU_LIMIT -z & # Limit new violating processes
done
done
CHANGE VARIABLES TO YOUR ENVIRONMENT NEEDS
CPU_LIMIT
Change this variable in above script if you would like to omit CPU consumption for every process to any other percentage then 20%. Please read "If using SMP computer" chapter bellow if you have SMP computer (more then 1 CPU or CPU with more then 1 core).
DAEMON_INTERVAL
Change this variable in above script if you would like to have more/less regular checking. Interval is in seconds and default is set to 3 seconds.
BLACK_PROCESS_LIST and WHITE_PROCESSES_LIST
Variable BLACK_PROCESSES_LIST limits only specified processes. If variable is empty (default) all violating processes are limited.
Variable WHITE_PROCESSES_LIST limits all processes except processes defined in this variable. If variable is empty (default) all violating processes are limited.
One or both of the variables BLACK_PROCESSES_LIST and WHITE_PROCESSES_LIST has to be empty - it is not logical that both variables are defined.
You can specify multiple processes in one of this two variables using delimiter characters "|" (without double quotes). Sample: if you would like to cpulimit all processes except mysql, firefox and gedit processes set variable: WHITE_PROCESSES_LIST="mysql|firefox|gedit"
PROCEDURE TO AUTOMATICALLY START DAEMON AT BOOT TIME
Set file permissions for root user:
Code:
sudo chmod 755 /usr/bin/cpulimit_daemon.sh
Open text editor with root privileges and save bellow script to new file /etc/init.d/cpulimit
Code:
#!/bin/sh
#
# Script to start CPU limit daemon
#
set -e
case "$1" in
start)
if [ $(ps -eo pid,args | gawk '$3=="/usr/bin/cpulimit_daemon.sh" {print $1}' | wc -l) -eq 0 ]; then
nohup /usr/bin/cpulimit_daemon.sh >/dev/null 2>&1 &
ps -eo pid,args | gawk '$3=="/usr/bin/cpulimit_daemon.sh" {print}' | wc -l | gawk '{ if ($1 == 1) print " * cpulimit daemon started successfully"; else print " * cpulimit daemon can not be started" }'
else
echo " * cpulimit daemon can't be started, because it is already running"
fi
;;
stop)
CPULIMIT_DAEMON=$(ps -eo pid,args | gawk '$3=="/usr/bin/cpulimit_daemon.sh" {print $1}' | wc -l)
CPULIMIT_INSTANCE=$(ps -eo pid,args | gawk '$2=="cpulimit" {print $1}' | wc -l)
CPULIMIT_ALL=$((CPULIMIT_DAEMON + CPULIMIT_INSTANCE))
if [ $CPULIMIT_ALL -gt 0 ]; then
if [ $CPULIMIT_DAEMON -gt 0 ]; then
ps -eo pid,args | gawk '$3=="/usr/bin/cpulimit_daemon.sh" {print $1}' | xargs kill -9 # kill cpulimit daemon
fi
if [ $CPULIMIT_INSTANCE -gt 0 ]; then
ps -eo pid,args | gawk '$2=="cpulimit" {print $1}' | xargs kill -9 # release cpulimited process to normal priority
fi
ps -eo pid,args | gawk '$3=="/usr/bin/cpulimit_daemon.sh" {print}' | wc -l | gawk '{ if ($1 == 1) print " * cpulimit daemon can not be stopped"; else print " * cpulimit daemon stopped successfully" }'
else
echo " * cpulimit daemon can't be stopped, because it is not running"
fi
;;
restart)
$0 stop
sleep 3
$0 start
;;
status)
ps -eo pid,args | gawk '$3=="/usr/bin/cpulimit_daemon.sh" {print}' | wc -l | gawk '{ if ($1 == 1) print " * cpulimit daemon is running"; else print " * cpulimit daemon is not running" }'
;;
esac
exit 0
Change file's owner to root:
Code:
sudo chown root:root /etc/init.d/cpulimit
Change permissions:
Code:
sudo chmod 755 /etc/init.d/cpulimit
Add script to boot-up procedure directories:
Code:
sudo update-rc.d cpulimit defaults
Reboot to check if script starts cpulimit daemon at boot time:
Code:
sudo reboot
MANUALLY CHECK, STOP, START AND RESTART DAEMON
Note: Daemon and service in this tutorial has equal meaning.
Note: For users using prior to Ubuntu 8.10 (like Ubuntu 8.04 LTS) instead of service command use "sudo /etc/init.d/cpulimit status/start/stop/restart" syntax or install sysvconfig package using command: sudo apt-get install sysvconfig
Check if cpulimit service is running
Check command returns: "cpulimit daemon is running" if service is running, or "cpulimit daemon is not running" if service is not running.
Code:
sudo service cpulimit status
Start cpulimit service
You can manually start cpulimit daemon which will start to omit CPU consumption.
Code:
sudo service cpulimit start
Stop cpulimit service
Stop command stops cpulimit daemon (so no new process will be limited) and also sets to all existing limited processes to have full access to CPU, just like it was before cpulimit was not running.
Code:
sudo service cpulimit stop
Restart cpulimit service
If you change some variables settings in /usr/bin/cpulimit_daemon.sh like CPU_LIMIT, DAEMON_INTERVAL, BLACK_PROCESSES_LIST or WHITE_PROCESSES_LIST, then after changing settings you must restart service.
Code:
sudo service cpulimit restart
CHECK CPU CONSUMPTION WITH OR WITHOUT CPULIMIT DAEMON
Without daemon
1. stop cpulimit daemon (sudo service cpulimit stop)
2. execute CPU intensive tasks in background
3. execute command: top and check for %CPU column
Result of %CPU is probably more then 20% for each process.
With daemon turned on
1. start cpulimit daemon (sudo service cpulimit start)
2. execute the same CPU intensive tasks in background
3. execute command: top and check for %CPU column
Result of %CPU should be maximum 20% for each process.
Note: Don't forget at beginning %CPU can be more then 20%, because daemon has to catch violating process in interval of 3 seconds (set in script by default)
IF USING SMP COMPUTER
I have tested this code on Intel dual-core CPU computer - that behaves like SMP computer. Don't forget that top command and also cpulimit by default behaves in Irix mode, where 20% means 20% of one CPU. If there are two CPUs (or dual-core) then total %CPU can be 200%. In top command Irix mode can be turned off with command I (pressing +i when top command is running) and Solaris mode is turned on, where total amount of CPU is divided by number of CPUs, so %CPU can be no more then 100% on any number of CPU computer. Please read more info about top command in top man page (search for I command). Please also read more about how cpulimit is operating on SMP computer in cpulimit official page.
But how does cpulimit daemon operates on SMP computer? Always in Irix mode. So if you would like to spend 20% of CPU power on 2-CPU computer then 40% should be used for CPU_LIMIT variable in cpulimit daemon script.
UNINSTALL CPULIMIT DAEMON AND CPULIMIT PROGRAM
If you would like to get rid of cpulimit daemon you can clean up your system by removing cpulimit daemon and uninstalling cpulimit program.
Stop cpulimit daemon
Code:
sudo service cpulimit stop # Stop cpulimit daemon and all cpulimited processes
Remove daemon from boot-up procedure
Code:
sudo update-rc.d -f cpulimit remove # Remove symbolic links
Delete boot-up procedure
Code:
sudo rm /etc/init.d/cpulimit # Delete cpulimit boot-up script
Delete cpulimit daemon
Code:
sudo rm /usr/bin/cpulimit_daemon.sh # Delete cpulimit daemon script
Uninstall cpulimit program
Code:
sudo apt-get remove cpulimit
Uninstall gawk program
If you don't need this program for any other script, you can remote it.
Code:
sudo apt-get remove gawk
NOTE ABOUT AUTHORS
I have just written daemon for cpulimit (bash scripts above). I am not the author of cpulimit project. If you need more info about cpulimit program, please read official cpulimit web page: http://cpulimit.sourceforge.net/.
Regards,
Abcuser
I had a similar problem, and the other solutions presented in the thread don't address it at all. My solution works for me right now, but it is suboptimal, particularly for the cases where the process is owned by root.
My workaround for now is to try very hard to make sure that I don't have any long-running processes owned by root (like have backup be done only as a user)
I just installed the hardware sensors applet for gnome, and set up alarms for high and low temperatures on the CPU, and then set up the following commands for each alarm:
low:
mv /tmp/hogs.txt /tmp/hogs.txt.$$ && cat /tmp/hogs.txt.$$ | xargs -n1 kill -CONT
high:
touch /tmp/hogs.txt && ps -eo pcpu,pid | sort -n -r | head -1 | gawk '{ print $2 }' >> /tmp/hogs.txt && xargs -n1 kill -STOP < /tmp/hogs.txt
The good news is that my computer no longer overheats and crashes. The downside is that terminal processes get disconnected from the terminal when they get stopped, and don't get reconnected when they get the CONT signal. The other thing is that if it was an interactive program that caused the overheating (like a certain web browser plugin!) then it will freeze in the middle of what I'm doing while it waits for the CPU to cool off. It would be nicer to have CPU scaling take care of this at a global level, but the problem is that I only have two selectable settings on my CPU and the slow setting isn't slow enough to prevent overheating.
Just to re-iterate here, this has nothing at all to do with process priority, re-nicing,and obviously nothing to do with stopping jobs that run for a long time. This has to do with preventing CPU utilization from staying at 100% for too long, because the hardware is unable to dissipate the heat quickly enough when running at full capacity (idle CPU generates less heat than a fully loaded CPU).
Some other obvious possibilities that might help are:
Lower the CPU speed overall in the BIOS
Replace the heatsink or re-apply the thermal gel to see if that helps
Clean the heatsink with some compressed air
Replace the CPU fan
[edit]
Note: no more overheating at 100% CPU when I disable variable fan speed in the bios (asus p5q pro turbo). With the CPU fully loaded, each core tops out at 49 celcius.
Using cgroups' cpu.shares does nothing that a nice value wouldn't do. It sounds like you want to actually throttle the processes, which can definitely be done.
You will need to use a script or two, and/or edit /etc/cgconfig.conf to define the parameters you want.
Specifically, you want to edit the values cpu.cfs_period_us and cpu.cfs_quota_us. The process will then be allowed to run for cpu.cfs_quota_us microseconds per cpu.cfs_period_us microseconds.
For example:
If cpu.cfs_period_us = 50000 and cpu.cfs_quota_us = 10000 then the process will receive 20% of the CPU time maximum, no matter what else is going on.
In this screenshot I have given the process 2% of CPU time:
As far as the process is concerned it is running at 100%.
Settings cpu.shares on the other hand can and will still use 100% of the idle CPU time.
In this similar example I have given the process cpu.shares = 100 (of 1024):
As you can see the process is still consuming all the idle CPU time.
References:
http://manpages.ubuntu.com/manpages/precise/man5/cgconfig.conf.5.html
http://kennystechtalk.blogspot.co.uk/2015/04/throttling-cpu-usage-with-linux-cgroups.html
In a system that uses systemd, you can run a single process with a maximum CPU usage using a command like the following:
sudo systemd-run --scope --uid=1000 -p CPUQuota=20% my_heavy_computation.sh
This will use up to 20% of a single CPU core (or CPU thread if using hyper-threading).
I also had the need to limit CPU time for certain processes. Cpulimit is a good tool, but I always had to manually find out the PID and manually start cpulimit, so I wanted something more convenient.
I came up with this bash script:
#!/bin/bash
function lp
{
ps aux | grep $1 | termsql "select COL1 from tbl" > /tmp/tmpfile
while read line
do
TEST=`ps aux | grep "cpulimit -p $line" | wc -l`
[[ $TEST -eq "2" ]] && continue #cpulimit is already running on this process
cpulimit -p $line -l $2
done < /tmp/tmpfile
}
while true
do
lp gnome-terminal 5
lp system-journal 5
sleep 10
done
This example limits the cpu time of each gnome-terminal instance to 5% and the cpu time of each system-journal instance to 5% as well.
I used another script I created named termsql in this example to extract the PID . You can get it here:
https://gitorious.org/termsql/termsql/source/master:
You can limit the amount of cpu time with cgroups. The OS will handle resource management just like you ask for in you question.
Here is a wiki with examples: https://wiki.archlinux.org/index.php/Cgroups
Since the processes already run as a separate user limiting all process from that user should be the easiest solution.
I see at least two options:
Use "ulimit -t" in the shell that creates your process
Use "nice" at process creation or "renice" during runtime
PS + GREP + NICE
The nice command will probably help.
This can be done using setrlimit(2) (specifically by setting RLIMIT_CPU parameter).
Throwing some sleep calls in there should force the process off the CPU for a certain time. If you sleep 30 seconds once a minute, your process shouldn't average more than 50% CPU usage during that minute.
I dont really see why you want to limit the CPU time... you should limit the total load on that machine, and the load is determined by IO operations mostly .
Ex: if i create a while(1){} loop, it will get the total load to 1.0, but if this loop does some disk writes the load jumps to 2.0... 4.0. And that's what killing your machine, not the CPU usage. The CPU usage can be easily handled by nice/renice.
Anyways, you could make a script that does a 'kill -SIGSTOP PID' for a specific PID, when the load gets too high, and kill -SIGCONT when everything gets back to normal... The PID's can be determined by using the 'px aux' command, because i see that it displays the CPU usage, and you should be able to sort the list using that column. I think this the whole thing could be done in bash...
You could scale down the CPU frequency. Then you don't have to worry about the individual processes. When you need more cpu's, scale the frequency back up.