Avi Kivity wrote: > On 03/24/2010 02:50 PM, Joerg Roedel wrote: >> >>> You can always provide the kernel and module paths as command line >>> parameters. It just won't be transparently usable, but if you're using >>> qemu from the command line, presumably you can live with that. >>> >> I don't want the tool for myself only. A typical perf user expects that >> it works transparent. >> > > A typical kvm user uses libvirt, so we can integrate it with that. > >>>> Could be easily done using notifier chains already in the kernel. >>>> Probably implemented with much less than 100 lines of additional code. >>>> >>> And a userspace interface for that. >>> >> Not necessarily. The perf event is configured to measure systemwide kvm >> by userspace. The kernel side of perf takes care that it stays >> system-wide even with added vm instances. So in this case the consumer >> for the notifier would be the perf kernel part. No userspace interface >> required. >> > > Someone needs to know about the new guest to fetch its symbols. Or do > you want that part in the kernel too? How about we add a virtio "guest file system access" device? The guest would then expose its own file system using that device. On the host side this would simply be a -virtioguestfs unix:/tmp/guest.fs and you'd get a unix socket that gives you full access to the guest file system by using commands. I envision something like: SEND: GET /proc/version RECV: Linux version 2.6.27.37-0.1-default (geeko@buildhost) (gcc version 4.3.2 [gcc-4_3-branch revision 141291] (SUSE Linux) ) #1 SMP 2009-10-15 14:56:58 +0200 Now all we need is integration in perf to enumerate virtual machines based on libvirt. If you want to run qemu-kvm directly, just go with --guestfs=/tmp/guest.fs and perf could fetch all required information automatically. This should solve all issues while staying 100% in user space, right? Alex -- 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
