[libvirt] [RFC] Data in the <topology> element in the capabilities XML
Peter Krempa
pkrempa at redhat.com
Thu Jan 17 16:14:30 UTC 2013
On 01/17/13 16:43, Daniel P. Berrange wrote:
>> I beg to differ:
>>
>> "This technology is informally called CMT (Clustered Multi-Thread)
>> and formally called "module" by the AMD's marketing service, but
>> whose real name is "Clustered Integer" Core Technology. In terms of
>> hardware complexity and functionality, this "module" is midway
>> between a true dual-core processor and its integer power (each
>> thread having a fully independent integer core) and a single core
>> processor that has the SMT ability, which can create a dual threads
>> processor but with the power of one (each thread shares the
>> resources of the core with the other thread)."
>>
>> (source: http://en.wikipedia.org/wiki/Bulldozer_(microarchitecture)#BULLDOZER_Core_.28aka_Module.29
>> )
>>
>> oVirt/vdsm considers the "Module" as a core with two threads, where
>> others consider it more as separate cores. The performance depends
>> on the type of task that is being run on the module.
>
> So what information does VDSM use to identify this hardware topology.
>
VDSM uses the <topology> element (subelement of cpu) in the capabilities
and multiplies the numbers by the number of numa nodes. As the data
there is taken from nodeinfo, this breaks on some systems.
>
> In some form or another we need to be providing the more detailed and
> accurate topology infomation in the capabilities NUMA description.
>
> What does 'hwloc --no-io --no-caches' shown on a Bulldozer machine ?
# hwloc-info --no-io --no-caches
depth 0: 1 Machine (type #1)
depth 1: 2 Socket (type #3)
depth 2: 4 NUMANode (type #2)
depth 3: 32 Core (type #5)
depth 4: 32 PU (type #6)
hwloc recognizes it as cores ...
# lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 32
On-line CPU(s) list: 0-31
Thread(s) per core: 2
Core(s) per socket: 8
Socket(s): 2
... lscpu as as threads ...
NUMA node(s): 4
Vendor ID: AuthenticAMD
CPU family: 21
Model: 1
Stepping: 2
CPU MHz: 1400.000
BogoMIPS: 4389.80
Virtualization: AMD-V
L1d cache: 16K
L1i cache: 64K
L2 cache: 2048K
L3 cache: 6144K
NUMA node0 CPU(s): 0-7
NUMA node1 CPU(s): 8-15
NUMA node2 CPU(s): 16-23
NUMA node3 CPU(s): 24-31
>
> Daniel
>
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