I did some more testing and it turns out to be a kernel error, introduced somewhere around linux 4.3.
Short description of the error: 100% cpu usage while using 3d in a vm with vfio My last known good kernel is 4.2.8, which gives me about 20% cpu usage while playing Diablo III. My first known bad kernel is 4.3.3, which gives me 100% cpu usage with every game, even while idle-ling in the menu. I tried to bisect it, but apparently during the 4.3 merge window vfio was completely broken, my VM won't even boot. Can someone give me a hint on how to debug this? I am not really capable of debugging the kernel, therefore bisecting was my only hope... Regards, Friedrich On 01/17/2016 10:29 AM, Friedrich Oslage wrote: > Hi, > > my host system is linux-4.4.0 with qemu-2.5.0 and a 4-core i7. Linux is > booted with isolcpus=1-3,5-7 to reserve 3 cores + threads for the > Windows 10 VM. > The VM's 3 cores(2 threads each) are pinned to the respective physical > core/thread. The iothread is pinned to 1-3,5-7. > > When i start a simple "openssl speed" in the VM and use the task manager > to pin it to a single cpu, it work's just the way I expect it to work: 1 > cpu has 100% usage, visible in both guest's task manager and host's top. > > But when I start a game, for instance Diablo 3 or CoD Black Ops III, and > also use the task manager to pin it to a single cpu, the cpu usage shown > in guest's task manager differs from the one shown in host's top: the > guest shows 1 cpu with 100% usage, as expected, but the host shows all 6 > cpus with 100% usage. > > It only happens with games. If you use other multi-threaded programs > without 3D, for instance prime95, the cpu usage in guest's task manager > is equal to the one in top. > > I can only assume vfio is somehow causing this additional cpu usage, but > a it seems to be.... to much. > > Did someone else experience this or can enlighten me on what qemu/vfio > is doing with additional cpu time? > > Regards, > Friedrich > > _______________________________________________ > vfio-users mailing list > vfio-users@redhat.com > https://www.redhat.com/mailman/listinfo/vfio-users _______________________________________________ vfio-users mailing list vfio-users@redhat.com https://www.redhat.com/mailman/listinfo/vfio-users
