On 08/27/2012 08:50 AM, Michael Wolf wrote: > On Sat, 2012-08-25 at 19:36 -0400, Glauber Costa wrote: >> On 08/24/2012 11:11 AM, Michael Wolf wrote: >>> On Fri, 2012-08-24 at 08:53 +0400, Glauber Costa wrote: >>>> On 08/24/2012 03:14 AM, Michael Wolf wrote: >>>>> This is an RFC regarding the reporting of stealtime. In the case of >>>>> where you have a system that is running with partial processors such as >>>>> KVM the user may see steal time being reported in accounting tools such >>>>> as top or vmstat. This can cause confusion for the end user. To >>>>> ease the confusion this patch set adds a sysctl interface to set the >>>>> cpu entitlement. This is the percentage of cpu that the guest system is >>>>> expected to receive. As long as the steal time is within its expected >>>>> range it will show up as 0 in /proc/stat. The user will then see in the >>>>> accounting tools that they are getting a full utilization of the cpu >>>>> resources assigned to them. >>>>> >>>> >>>> And how is such a knob not confusing? >>>> >>>> Steal time is pretty well defined in meaning and is shown in top for >>>> ages. I really don't see the point for this. >>> >>> Currently you can see the steal time but you have no way of knowing if >>> the cpu utilization you are seeing on the guest is the expected amount. >>> I decided on making it a knob because a guest could be migrated to >>> another system and it's entitlement could change because of hardware or >>> load differences. It could simply be a /proc file and report the >>> current entitlement if needed. As things are currently implemented I >>> don't see how someone knows if the guest is running as expected or >>> whether there is a problem. >>> >> >> Turning off steal time display won't get even close to displaying the >> information you want. What you probably want is a guest-visible way to >> say how many miliseconds you are expected to run each second. Right? > > It is not clear to me how knowing how many milliseconds you are > expecting to run will help the user. Currently the users will run top > to see how well the guest is running. If they see _any_ steal time some > users think they are not getting the full use of their processor > entitlement. > And your plan is just to selectively lie about it, but disabling it with a knob? > Maybe I'm missing what you are proposing, but even if you knew the > milliseconds that you were expecting for your processor you would have > to adjust the top output in your head so to speak. You would see the > utilization and then say 'ok that matches the number of milliseconds I > expected to run..." If we take away the steal time (as long as it is > equal to or less than the expected amount of steal time) then the user > running top will see the 100% utilization. > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
