On Wed, 2013-03-06 at 12:13 +0400, Glauber Costa wrote: > On 03/06/2013 05:41 AM, Marcelo Tosatti wrote: > > On Tue, Mar 05, 2013 at 02:22:08PM -0600, Michael Wolf wrote: > >> Sorry for the delay in the response. I did not see the email > >> right away. > >> > >> On Mon, 2013-02-18 at 22:11 -0300, Marcelo Tosatti wrote: > >>> On Mon, Feb 18, 2013 at 05:43:47PM +0100, Frederic Weisbecker wrote: > >>>> 2013/2/5 Michael Wolf <mjw@xxxxxxxxxxxxxxxxxx>: > >>>>> In the case of where you have a system that is running in a > >>>>> capped or overcommitted environment the user may see steal time > >>>>> being reported in accounting tools such as top or vmstat. This can > >>>>> cause confusion for the end user. > >>>> > >>>> Sorry, I'm no expert in this area. But I don't really understand what > >>>> is confusing for the end user here. > >>> > >>> I suppose that what is wanted is to subtract stolen time due to 'known > >>> reasons' from steal time reporting. 'Known reasons' being, for example, > >>> hard caps. So a vcpu executing instructions with no halt, but limited to > >>> 80% of available bandwidth, would not have 20% of stolen time reported. > >> > >> Yes exactly and the end user many times did not set up the guest and is > >> not aware of the capping. The end user is only aware of the performance > >> level that they were told they would get with the guest. > >>> But yes, a description of the scenario that is being dealt with, with > >>> details, is important. > >> > >> I will add more detail to the description next time I submit the > >> patches. How about something like,"In a cloud environment the user of a > >> kvm guest is not aware of the underlying hardware or how many other > >> guests are running on it. The end user is only aware of a level of > >> performance that they should see." or does that just muddy the picture > >> more?? > > > > So the feature aims for is to report stolen time relative to hard > > capping. That is: stolen time should be counted as time stolen from > > the guest _beyond_ hard capping. Yes? > > > > Probably don't need to report new data to the guest for that. > > > If we take into account that 1 second always have one second, I believe > that you can just subtract the consigned time from the steal time the > host passes to the guest. > > During each second, the numbers won't sum up to 100. The delta to 100 is > the consigned time, if anyone cares. > > Adopting this would simplify this a lot. All you need to do, really, is > to get your calculation right from the bandwidth given by the cpu > controller. Subtract it in the host, and voila. I looked at doing that once but was told that I was changing the interface in an unacceptable way, because now I was not reporting all of the elapsed time. I agree it would make things simpler. > > -- 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
