[vfio-users] CPU pinning with cgroups

[Garrett Powell]

Now I think I finally understand. I'll try using libvirt. Just one question:

Is it possible to set up libvirt using my existing raw hard drive image?
I've set it up as shown in Alex's blog (substituting a new image with my
existing one), but I'm getting a BSOD with an "inaccessible boot device"
error on boot. Windows startup repair hasn't done anything.

Thanks

On Tue, Sep 8, 2015 at 12:15 AM Jon Panozzo <jonp at lime-technology.com>
wrote:

> Just to second Alex's point here, I see a lot of folks doing QEMU the old
> fashioned way, which is to say, manual invocation.  Libvirt really is an
> amazing management solution and makes things so much easier.  Lots of
> things can go awry if you're invoking QEMU manually, and libvirt can
> prevent that, as well as automate many other aspects of management that
> manual QEMU invocation cannot.
> On Sep 7, 2015 3:20 PM, "Alex Williamson" <alex.l.williamson at gmail.com>
> wrote:
>
>> On Sun, Sep 6, 2015 at 7:19 PM, Garrett Powell <
>> garretttracypowell at gmail.com> wrote:
>>
>>> I've been having trouble with my guest freezing up, which I'm told is
>>> due to a lack of CPU pinning. I'm currently trying to set up CPU pinning
>>> with cgroups (specifically cpuset), but the freezing isn't going away.
>>> Could anyone tell me what I'm doing wrong? I'm specifically referring to
>>> the *cgcreate*, *cgset *and* cgexec* lines. Here's my launch script:
>>>
>>> #!/bin/bash
>>>
>>> export QEMU_AUDIO_DRV=pa
>>> export QEMU_PA_SERVER=localhost
>>> export PULSE_SERVER=localhost
>>>
>>> vfio-bind 0000:06:00.0
>>>
>>> synergys --daemon --config /etc/synergy.conf
>>>
>>> for i in {0..3}; do
>>>     echo performance >
>>> /sys/devices/system/cpu/cpu${i}/cpufreq/scaling_governor
>>> done
>>>
>>> echo 5120 > /proc/sys/vm/nr_hugepages
>>>
>>> cgcreate -g cpuset:kvm
>>> cgset -r cpuset.cpus=0-3 -r cpuset.mems=0 -r cpuset.cpu_exclusive=1 kvm
>>> cgexec -g cpuset:kvm qemu-system-x86_64 \
>>>
>>
>> Ok, so you've change to pCPUs 0-3 instead of 4-7, but doesn't this have
>> the same problem as your previous attempt with taskset?  You're using a
>> different tool, but afaict you're still not doing 1:1 pinning of vCPUs,
>> you're pining them to a set of pCPUs.  Taskset can work, but you need to
>> get the thread ID for each vCPU thread and pin it.  The problem is not the
>> tool you're using but how you're using it, to set the entire process and
>> all the threads it will launch to a range of CPUs rather than pulling out
>> the vCPU threads and individually pinning them.  There's this really great
>> tool that already does this, it's called libvirt.  Thanks,
>>
>> Alex
>>
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>>
>>
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