Linux : See CPU usage by a process for the last second

linuxmonitoringprocessps

vmstat 1

Above will print virtual memory statistics each seconds. It will also show the CPU utilization for last second.

I have a web server at hand which runs httpd and MySQL. I need to find how much CPU httpd consumed in last second. Like vmstat particularly for httpd.

I tried this :

ps -e -o %mem,%cpu,cmd | grep mysql | awk '{memory+=$1;cpu+=$2} END {print memory,cpu}'

But it will show me the ratio of CPU used since the start of the process.

So, with above, if my process caused a spike and then went to sleep for long time, I won't know it. It's like windows process manager, which shows which process is using how much CPU. I hope I am making my question understandable. I will clarify if anything is missing.

Best Answer

You could use top -b -d 1 to achieve that for CPU usage. top displays process CPU usage relative to the last output.

Related Solutions

Freebsd – Get CPU usage for single process

I don't have access to a BSD machine to check but your ps command should work as advertised. In any case, as a dirty hack, you could always just parse the output of the full ps (where NNN is the PID you are after):

ps aux | awk  -v OFS="\t" '$2=="NNN"'

Or, to keep the output format identical to that of ps:

ps aux | grep -i '^[a-z ]*NNN '

You may have to tweak the ps options a bit since they're different in BSD. Just use whichever combination prints all processes.

Linux – suspend a process (`stress`) to simulate memory pressure minus the CPU cost

I found this Oracle article about OOM Killer (Out Of Memory Killer) answer a half of your question, specially in 'Configuring the OOM Killer' chapter.
I extract from there two important commands (I think):

Disable OOM Killer root@host:~# sysctl vm.overcommit_memory=2
Exclude a process from OOM Killer root@host:~# echo -17 > /proc/<pid>/oom_adj

Other very interesting answer is 1.4 in this FAQ from stress project page, it says:

1.4 Why is my CPU getting hammered but not my RAM?

This is because stress if faily conservative in its default options. It is pretty easy to render a system temporarly unusable by forcing the virtual memory manager to thrash. So make sure you understand how much memory you have and then pass the appropriate options. On a dual-core Intel system with 3 GB of RAM a reasonable invocation is this:

stress -m 1 --vm-bytes 2G

Right, your question has not been answered yet. Let's look at stress manual ...

-c, --cpu N
spawn N workers spinning on sqrt()

Maybe the above option could help, try to set it to zero. Oops, It doesn't work!?

After a look at the code I noticed that this option is disabled by default. And I've also noticed that --vm-hang option may be what you want.

The default action of --vm is spinning on malloc()/free(), and it's CPU intensive! --vm-hang makes stress program do a pause for seconds every time it allocates until free().

Try to use the following (consumes ~128MB of RAM):
root@host:~# stress --vm 1 --vm-bytes 128000000 --vm-hang 3600
And do a test in another terminal:
root@host:~# top

Best Answer

Related Solutions

Freebsd – Get CPU usage for single process

Linux – suspend a process (`stress`) to simulate memory pressure minus the CPU cost

Related Question