On 8/21/07, Laurent Vivier <Laurent.Vivier@xxxxxxxx> wrote: > Glauber de Oliveira Costa wrote: > >> by doing this at kernel level, we can: > >> - measure exactly the guest time, > >> - move this part of system time to user time (as you think it should be > >> user time), > >> - have consistency between system, user and guest time, > >> - report values in /proc/state and /proc/<pid>/state, at system wide level > >> > >> I'm not sure we can measure the guest time at the qemu user level. > >> > >> Perhaps Rusty can say what he thinks about this ? > >> > > Even if we cannot _now_, isn't that an easier, and safer change? (and > > I don't think we lose anything by design). > > Could you explain ? How should I do this ? > I'm _sure_ it is not easier to do that at qemu level. > > I don't like to patch kernel (it is the last thing I do to solve a problem: I > know there is always at least one guy to not agree the patch :-P ) but in this > case I think this is the best way to do that. > > I think the virtualization notion should be introduced at the kernel level, at > least in the kernel statistics: it is generic, it can be used by other > virtualization tools. As I said, until know CPUs have got only two states > reflected in statistics by "user time" and "system time". Since recently, they > have introduced a third state, the virtual CPU, that, in my opinion, should be > also reflected in the CPU statistics as the "guest time". After a second thought on this, you seem to be right. > > > > Although I don't know KVM to a that deep level, I think it should be > > possible to keep the virtual cpus in different process (or threads), > > and take the accounting time from there. Perfectly possible to know > > the time we spent running (user time), and the time the hypervisor > > spent doing things on our behalf (system time). > > But we have always user time accounted as system time. CPU stats are wrong if we > do not modify the kernel. Can you live with wrong statistics ? (yes, I think, > you can, but perhaps someone else not) > No, I can't. Just because I suggested an alternate way (even if it was wrong), it does not mean I want things to be done wrongly. -- Glauber de Oliveira Costa. "Free as in Freedom" http://glommer.net "The less confident you are, the more serious you have to act." _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
