[SORTA OT] Getting CPU usage of a process

[Joe Van Dyk]

Hi,

I'd like to be able to get the CPU usage of a particular process.
What are my options for doing so from Ruby?

I've found the libgtop ruby binding, and I could use that, but I would
rather not bring in another dependency. This will run on Linux
systems only.

And would I want to use the elapsed real cpu time? Or the sum of the
elapsed user and system cpu time? (and then I believe I divide that
by the elapsed wall clock time)

Thanks,
Joe

[Kero]

man proc, look for "/proc/[number]/stat"
It contains a set of times spent by the process and its children.
it also contains the starttime, so this should allow you to compute "Cpu
usage of the process".

Hth,
Kero.

+--- Kero ---------------------------------- kero@chello@nl ---+
| The last good thing written in C++ was the Pachelbel Canon |
| Jerry Olson |
+--- M38c ------------ http://members.chello.nl/k.vangelder ---+

[Joe Van Dyk]

On 11/10/05, Kero <ke...@chello.single-dot.nl> wrote:
> > I'd like to be able to get the CPU usage of a particular process.
> > What are my options for doing so from Ruby?
> >
> > I've found the libgtop ruby binding, and I could use that, but I would
> > rather not bring in another dependency. This will run on Linux
> > systems only.
> >
> > And would I want to use the elapsed real cpu time? Or the sum of the
> > elapsed user and system cpu time? (and then I believe I divide that
> > by the elapsed wall clock time)
>
> man proc, look for "/proc/[number]/stat"
> It contains a set of times spent by the process and its children.
> it also contains the starttime, so this should allow you to compute "Cpu
> usage of the process".

Thanks, I'm aware of /procproc.

I want to be able to constantly keep the user updated on how much of
the cpu the application is using.

Would I take the sum of the elapsed user and system cpu time and
divide that by the elapsed wall clock time to get the current cpu
percentage?

[Joe Van Dyk]

And one other question, does anyone know how I might do this on
Windows via Ruby?

[x1]

Seems to be lots of win32ole stuff that's usefull here:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wmisdk/wmi/wmi_tasks__performance_monitoring.asp

this seems tto work ok on a process name but.. not sure how to do it on an id..
wscript.exe test.vbs
-------test.vbs-------
strComputer = "."
Set objWMIService = GetObject("winmgmts:" _
& "{impersonationLevel=impersonate}!\\" _
& strComputer & "\root\cimv2")
set PerfProcess = objWMIService.Get(_
"Win32_PerfFormattedData_PerfProc_Process.Name='Idle'")

While (True)
PerfProcess.Refresh_
Wscript.Echo PerfProcess.PercentProcessorTime
Wscript.Sleep 1000
Wend
--------/test.vbs--------

[Kero]

>> > I'd like to be able to get the CPU usage of a particular process.
>> > What are my options for doing so from Ruby?
>> >

>> > And would I want to use the elapsed real cpu time? Or the sum of the
>> > elapsed user and system cpu time? (and then I believe I divide that
>> > by the elapsed wall clock time)
>>
>> man proc, look for "/proc/[number]/stat"
>> It contains a set of times spent by the process and its children.
>> it also contains the starttime, so this should allow you to compute "Cpu
>> usage of the process".
>

> Would I take the sum of the elapsed user and system cpu time and
> divide that by the elapsed wall clock time to get the current cpu
> percentage?

That's what I would start with.

Then you'll want to remember values of 'some time ago' so you can do the
computation 'over the last some-time', as well as 'from the start of the
process'.