[Xen-devel] xl vcpu-pin peculiarities in core scheduling mode

[Sergey Dyasli <sergey.dyasli@citrix.com>]

Hi Juergen,

I've notived there is no documentation about how vcpu-pin is supposed to work
with core scheduling enabled. I did some experiments and noticed the following
inconsistencies:

  1. xl vcpu-pin 5 0 0
     Windows 10 (64-bit) (1)              5     0    0   -b-    1644.0  0 / all
     Windows 10 (64-bit) (1)              5     1    1   -b-    1650.1  0 / all
                                                     ^                  ^
     CPU 1 doesn't match reported hard-affinity of 0. Should this command set
     hard-affinity of vCPU 1 to 1? Or should it be 0-1 for both vCPUs instead?


  2. xl vcpu-pin 5 0 1
     libxl: error: libxl_sched.c:62:libxl__set_vcpuaffinity: Domain 5:Setting vcpu affinity: Invalid argument
     This is expected but perhaps needs documenting somewhere?


  3. xl vcpu-pin 5 0 1-2
     Windows 10 (64-bit) (1)              5     0    2   -b-    1646.7  1-2 / all
     Windows 10 (64-bit) (1)              5     1    3   -b-    1651.6  1-2 / all
                                                     ^                  ^^^
     Here is a CPU / affinity mismatch again, but the more interesting fact
     is that setting 1-2 is allowed at all, I'd expect CPU would never be set
     to 1 with such settings.

Please let me know what you think about the above cases.

--
Thanks,
Sergey