On Wed, Jun 13, 2012 at 8:23 AM, Emmanuel Noobadmin <centos.admin@xxxxxxxxx> wrote: > On 6/12/12, Stefan Hajnoczi <stefanha@xxxxxxxxx> wrote: > > Further tests done on the following set only >>> qemu-kvm-0.12.1.2-2.209.el6_2.4.x86_64 >>> on SLES 6, 2.6.32-220.7.1.el.x86_64 (Intel 82801JI ICH10) > >>> 1. VMM add physical host usb device -> select storage to guest >>> 2. VMM remove hardware >>> 3. Physically remove the USB storage from the host, thread/core >>> assigned to guest goes 100% >> >> Two clarifications: >> >> 1. Can you confirm that the 100% CPU utilization only happens in Step >> #3? For example, if it happened in Step #2 that would suggest the >> guest is entering a loop. Step #3 suggests the host is entering a >> loop. > > Verified Step #3 triggers the issue. > >> 2. Please run top(1) on the host during high CPU utilization to >> confirm which process is causing high CPU utilization. > > Verified is the VM's process. If unpinned, the utilization floats > around the cores, if pinned, the 100% load stays with the physical > core. Load on the core stabilizes at around 32% usr 67% sys if the VM > is active. Pausing the VM makes it go to around 80+ sys. Since system time is a large chunk you could use strace -f -p $(pgrep qemu-kvm) or other system call tracing tools to see what the qemu-kvm process is doing. You didn't say that the guest is frozen, so QEMU is probably not in an infinite loop. Instead it may be that we have a USB device file descriptor in select(2) and continually read -ENODEV or similar from it. So the guest can make progress but you see high %sys CPU load on the host. strace(1) can confirm what's going on. Stefan -- 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
