On 2009-09-07 16:31, ChadDavis wrote:
I'm using the gnome-system-monitor to watch some apps and their
resource usage. On the process view, it lists a %CPU column. I
assume this means the percentage of the CPU that the application is
currently using. THe documentation doesn't really clarify this, but
seems not to contradict this interpretation.
The app I'm watching frequently hits 40-60 percent CPU usage. My
question is about interpreting this. I'm testing on a Core2 Duo
machine. My understanding of computer architecture is not great, but
not trivial. Here's what I'm thinking. If one cpu is idle, and an
app gets to run, it's going to get 100% of the cpu, correct? Even if
it's only executing a 100 instructions, if there's no contention for
the CPU, the app will have 100% of the CPU for however small of an
interval it takes to execute those instructions, correct? I'm
certainly not familiar with the linux internals of my debian system
enough
*When it's running*, it gets 100% of a CPU.
But on a multiprocessing, multiuser computer, where other processes
and the OS are competing for time, your app only gets full use of
the CPU for a few milliseconds and then the OS takes it away and
gives it to another process. Also, when your app is waiting on IO
(from disk, network, keyboard, etc) it's not doing anything.
So, that 40-60% seems right.
If you want to see the CPU burn, try this simple Python script:
### BEGIN
i = -2 * 10**9
while 1: i = i + 1
### END
(Note the extra <Enter> you must press after the 2nd line!)
If someone can shed some light on this, as well as pointing me towards
some information and tools about how to better judge application
performance, I'd appreciate it.
--
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