Re: Question on measuring CPU Usage in Linux
On Tue, Mar 25, 2008 at 12:00 PM, CHAPLIN, JAMES (CTR) [EMAIL PROTECTED] wrote: We are using RHEL 5.0 4.5 (pending if using Oracle or not). So I am assuming the information form PERFKIT is the best measure of CPU Usage? That probably means you have a 2.6 kernel and your CPU usage is already broken up into more components than the ones you mention. Maybe your tools are based on 2.4 kernels and don't show you all. Performance Toolkit may be able to tell you how much the virtual machine was using, but not why or how. AFAIK the technology to feed it with information about Linux internals is neither strategic nor attractive. I am trying to understand the waiting for I/O value of CPU, is this CPU unable to process other work? The Linux perception is that it is waiting for I/O. But only the VM data can reveal whether that is really true. I can certainly think of situations where lack of CPU or memory on z/VM will make Linux think it is waiting for the disk I/O. That's not a problem for Linux because it really does not need to know these details (virtualization is also about hiding details from the guest). But it is a problem for the performance analyst who wants to tune his Linux on z/VM configuration. That's why we claim you need to see both sides of the equation. Rob -- Rob van der Heij Velocity Software GmbH http://velocitysoftware.com/ -- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Re: Question on measuring CPU Usage in Linux
We are using RHEL 5.0 4.5 (pending if using Oracle or not). So I am assuming the information form PERFKIT is the best measure of CPU Usage? I am trying to understand the waiting for I/O value of CPU, is this CPU unable to process other work? James Chaplin Systems Programmer, MVS, zVM zLinux Base Technologies, Inc (703) 921-6220 -Original Message- From: Linux on 390 Port [mailto:[EMAIL PROTECTED] On Behalf Of Mark Post Sent: Monday, March 24, 2008 5:37 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: Question on measuring CPU Usage in Linux On Mon, Mar 24, 2008 at 4:04 PM, in message [EMAIL PROTECTED], CHAPLIN, JAMES (CTR) [EMAIL PROTECTED] wrote: Under Linux we have the command vmstat (and others) that display the CPU usage. What version of what distribution do you have? Anything prior to SLES10 and RHEL5, the data from inside the guest is pretty much meaningless. Mark Post -- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 -- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Re: Question on measuring CPU Usage in Linux
On Mar 25, 2008, at 9:28 AM, Stephen Frazier wrote: The numbers given by PERFKIT are mostly meaningless. They're much less meaningless than the vmstat/top numbers. I mean, that's damning with faint praise, maybe, but Adam -- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Re: Question on measuring CPU Usage in Linux
On Tuesday, 03/25/2008 at 10:30 EDT, Stephen Frazier [EMAIL PROTECTED] wrote: The numbers given by PERFKIT are mostly meaningless. ...in the context of knowing what's going on *inside* Linux. You can't infer the performance profile of the virtual machine from Linux numbers, and you can't infer the performance profile of Linux processes by looking at virtual machine status. You can use a product such as ESALPS (Velocity Software) or OMEGAMON XE for z/VM and Linux (IBM) to correlate the two pieces of information. (I didn't want anyone thinking that Performance Toolkit gives meaningless numbers.) Alan Altmark z/VM Development IBM Endicott -- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Re: Question on measuring CPU Usage in Linux
The numbers reported by vmstat inside a Linux guest report on the virtual CPU usage. Unless you have attached real CPUs to a guest, they're not a good representation of real CPU utilization -- it tells you only what the division of labor is from Linux's perspective. Useful for determining whether you have an I/O hog or not, but not reflective of the actual usage of the system. If you are using Perfkit, you need to install RMFPM in the guest and configure Perfkit to accept data from it to get a better sense of what is actually going on. There are other solutions that use a different approach to correlate the VM and Linux CPU numbers (SNMP + VM accounting records), and recent mods to the Linux kernel (I think those made it into SLES 9 SP4, but don't know for certain -- they're in SLES 10 SP1) that provide more accurate VM accounting records, but I don't know if Perfkit supports them yet. Don't run RMFPM for very long; it's a real hog on it's own. -- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
Re: Question on measuring CPU Usage in Linux
On Mon, Mar 24, 2008 at 4:04 PM, in message [EMAIL PROTECTED], CHAPLIN, JAMES (CTR) [EMAIL PROTECTED] wrote: Under Linux we have the command vmstat (and others) that display the CPU usage. What version of what distribution do you have? Anything prior to SLES10 and RHEL5, the data from inside the guest is pretty much meaningless. Mark Post -- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
