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Re: [libvirt] PATCH: Support vCPU pinning in QEMU driver



On Fri, May 16, 2008 at 10:47:40PM +0100, Daniel P. Berrange wrote:
> KVM added ability to get the thread ID for vCPUs via the monitor
> 
> (qemu) info cpus
> * CPU #0: pc=0x00000000000ffff0 thread_id=11463
>   CPU #1: pc=0x00000000fffffff0 thread_id=11464
>   CPU #2: pc=0x00000000fffffff0 thread_id=11465
> 
> With this we have enough information to be able to support vCPU pinning in
> the QEMU driver for KVM. For QEMU/KQEMU it is trivial, since they have a
> single thread.
> 
> The following patch implements CPU pinning and fetching of CPU affinity
> information.  In this example I pin one of the 2 cpus in a guest:
[...]
> This is implemented using sched_setaffinity/sched_getaffinity which are 
> Linux specific. There doesn't appear to be a portable process affinity
> API in POSIX.

  looks fine to me. I guess the main use will be for KVM which is Linux 
specific, so that should not be a big deal IMHO (if we could just make sure
the code doesn't bomb at compile time on say Solaris).

> If the KVM instance does not support the 'thread_id' data in 'info cpus',
> we simply print out a suitable error message. We detect the mapping at
> startup and cache it thereafter.

  Hum, okay, seems that should work just fine even if one migrates or
save/restore.
  Is the error reported each time one starts a new VM ? 

  In any case looks fine, +1

Daniel

-- 
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Daniel Veillard      | virtualization library  http://libvirt.org/
veillard redhat com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
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