On Tuesday, September 30, 2014 01:44:48 PM Al Patel wrote:
> Hi:
>
> I am running qemu-kvm version 1.0
>
> ($kvm -version
> QEMU emulator version 1.0 (qemu-kvm-1.0), Copyright (c) 2003-2008 Fabrice
> Bellard)
>
> When I start a VM with 4 vcpus, I see about 8 threads. (the thread count
> varies ...)
>
> 1118 1118 ? 00:00:00 kvm-irqfd-clean
> *8767 8767 pts/4 00:03:16 kvm*
> * 8767 8770 pts/4 1-15:10:10 kvm*
> * 8767 8771 pts/4 1-14:40:42 kvm*
> * 8767 8772 pts/4 2-04:39:57 kvm*
> * 8767 8773 pts/4 08:35:51 kvm*
> * 8767 28585 pts/4 00:00:00 kvm*
> * 8767 28597 pts/4 00:00:00 kvm*
> * 8767 28598 pts/4 00:00:00 kvm*
> * 8767 28599 pts/4 00:00:00 kvm*
> * 8767 28600 pts/4 00:00:00 kvm*
> 8768 8768 ? 00:00:00 kvm-pit/8767
Probably aio emulation via a threadpool. Make sure you use aio=native and it
won't do that.
>
>
> On older version of qemu (prior to the qemu/kvm binary merge), I typically
> saw 5 threads (for 4 vcpu) - which I believe was 1 x 4 for each vcpu and
> 1 for
> the IO threads.
>
> In the current system, what are the extra threads?
>
> Secondly, I am currently not using libvirt and having to start qemu from
> command line. I still want to pin the vcpu to a pcpu and want to use
> taskset on a thread. Unless I know which thread is emulating the vcpu
> how can I pin that thread?
>
> Do you have any other thoughts on the pinning part?
In qmp, you can query the info about vcpus and host threads. ("info cpus" in
qemu monitor iirc).
>
> Any guidance/pointers?
>
> Thank You.
