OK.
The next kind of problem is performance issues.
Now troubleshooting performance is an art on its own.
And in RHCSA, it's not your mission
to be able to be perfectly capable of troubleshooting
performance.
But I want to give you a brief introduction
so that you know where you need to be looking.
So you should focus on four key areas of performance.
There's memory, there's CPU load, there's disk load,
and there is network.
And you can use STOP to get a generic image
of your performance and more specialized tools
only if you have a strong indication of what is wrong.
Now let me show you an example of a system that
does have a performance problem.
So performance-related problems always start from top.
I would say here we have the top interface
and do have a look at what is going on.
So what do we see?
We see a load average for the last minute of 1.73.
It's a little bit high on the two-CPU system.
But we can see that it decreases already a little bit.
And it's acceptable because this is a two-core system.
And we are below 2.00.
I don't see any zombies.
I don't see any significant CPU load.
As you can see, 90% idle.
That is good.
Now here I do see something that I don't like.
The memory, look at that, 716 meg total,
of which we have 53 free and only 128 of available.
And you can also see that STOP is being
used quite significantly.
Now for a system this low in memory,
the performance of the tools are quite good anyway.
But I think we found the performance problem here.
The performance problem is memory.
How are you going to fix it?
Well, you go to the hardware store.
Buy yourself some more memory.
Or if it's a virtual machine, allocate more memory
to the virtual machine.
For your information, I can show you
what I've done to simulate this problem.
That might be interesting.
So let me get out of here and reboot.
And in the group prompt, I've used the mem option.
So mem equals.
You can never allocate more memory
than what is physically present.
But if I use mem equals 2 gigs, then that
is what I get instead of 4 gigs, which
is allocated on this machine.
Might be very useful because that is something
that you can do to test your system
and see how it reacts in low memory environments.
Anyway, you have a performance problem.
TOP is the best way to get started.