Troubleshoot Performance | Into the Terminal 51

Critical Administration Skills for Red Hat Enterprise Linux: Whether you are new to Linux or new to RHEL, join our hosts for a hands-on look into the commands and processes, ask questions, and grow your knowledge.
Get Started with Red Hat Enterprise Linux: redhat.com/tryrhel
Twitter: / rhel
Eric The IT Guy: / itguyeric
Scott McBrien: / stabby_mc
Try it for yourself: lab.redhat.com
Troubleshoot Networking | Into the Terminal 50
• Troubleshoot Networkin...
Web Console | Into the Terminal 10
• Web Console | Into the...
Commands:
top, free, vmstat, iostat, strace, uptime
Chapters:
00:00 Stream start
00:26 Performance tools
07:26 The break
08:58 What is performance?
11:25 High load average
20:12 What is a process doing?
32:09 Metrics with web console
37:06 Wrap up

[@4vladimir]

Great, as usual!

[@bbk4685]

Thank you. This helps

[@naveenkumarshukla]

Ultimate troubleshooting

[@shanearchibald7940]

Thank you very much and this was good.

[@RedHatEnterpriseLinux]

Glad you enjoyed it!

[@scottmcbrien6535]

I totally forgot to stay on after the end graphic of the show to talk about how I introduced the problems we troubleshot today!
For messing with the load average, I just ran:
dd if=/dev/zero of=/dev/null &
a whole bunch of time (40 or so times). Because /dev/zero supplies a never-ending stream of null characters and /dev/null accepts all input but does nothing with it, the program will never end. Additionally, both /dev/zero and /dev/null are devices that exist in kernel memory, combine that with it not being computationally hard to move a single character from one place to another (but never actually store it), I was able to load up the system with 'processes' but not grind the system to a halt. That way, I could show a condition, but still have access to a reasonably responsive shell and other processes. Initially I thought I'd have to use nice to keep the shell responsive, but thankfully that was not needed.
The video covered the introduced DNS behavior pretty well. I wanted something that I could demonstrate strace against. I used the behavior of DNS to try to contact the first named DNS server first, then, if there is no response, move to the secondary DNS server listed in the file. If I wanted even more time waiting for curl to respond with data I could have added another bogus DNS server above the actual one provided by the dhcp lease.

[@Imrankhan-wl9lo]

If ps and top command hung on centos 7 but may be the cause and can you please help me with resolution?

[@RedHatEnterpriseLinux]

Something that immediately springs to mind is the server is completely locked up or your disk maybe full. - Eric

[@Imrankhan-wl9lo]

@@RedHatEnterpriseLinux So we need to restart is good option