[libvirt] RFC: add Intel CMT feature support

[Peter Krempa]

On Sat, Jun 27, 2015 at 03:45:21 +0000, Ren, Qiaowei wrote:
> Hi All,
> 
> Some Intel processor families (e.g. the Intel Xeon processor E5 v3 family) introduced some PQos (Platform Qos) features to monitor or control shared resource.
> 
>   - CMT (Cache Monitoring Technology): measure the usage of cache by applications running on the platform.
>   - CAT (Cache Allocation Technology): enable an OS or Hypervisor/VMM to specify the amount of cache space into which an application can fill.
>   - MBM (Memory Bandwidth Monitoring): build on the CMT infrastructure to allow monitoring of bandwidth from one level of the cache hierarchy to the next - in this case focusing on the L3 cache, which is typically backed directly by system memory. As a result of this implementation, memory bandwidth can be monitored.
> 
> For more information, see "Intel 64 and IA-32 Architectures Software Developer's Manual".
> 
> Among these PQos features, currently CMT patches has been merged into Linux kernel mainline. So this patch series proposed in this mail will focus on CMT feature support in libvirt.
> 
> At the library API layer, I plan on adding cache related field into virDomainInfo and virNodeInfo:
> 
> Add "cache" member into virNodeInfo to get total size of cache in one node.
> struct virNodeInfo {
>     ...
>     unsigned int cores;   /* number of cores per socket, total number of
>                              processors in case of unusual NUMA topology*/
>     unsigned int threads; /* number of threads per core, 1 in case of
>                              unusual numa topology */
> +  unsigned int cache;   /* cache size in bytes */

We don't allow changing/adding members to public structures. You
probably will be better of by adding this info to the capabilities XML.

> };
> 
> Add "cacheOcc" member into virDomainInfo to get cache occupancy for one VM.
> struct virDomainInfo {
>     ...
>     unsigned short nrVirtCpu;   /* the number of virtual CPUs for the domain */
>     unsigned long long cpuTime; /* the CPU time used in nanoseconds */
> +  unsigned long long cacheOcc; /* the cache occupancy in Bytes */

Neither this structure can be modified.

> };
> 
> With this change, those applications like OpenStack based on libvirt can collect cache usage for metering and monitoring (e.g. any VM using more than X% of cache).

You can use the bulk stats API (virDomainListGetStats) to add this field
since that uses the typed parameter approach which can be extended.

> 
> Because CMT implementation in Linux kernel is based on perf mechanism and there is no nice and public API library for perf, I have to wrapper system call for perf in libvirt to use CMT feature, and enable/disable perf event for CMT when VM is created/destroyed.
> 
> Any thoughts on this plan before I start submitting code patches? Do you think whether I need add several new APIs and XML element for CMT feature (or more PQos features)?
> 
> Thanks,
> Qiaowei

Peter
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: Digital signature
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20150629/e937bffd/attachment-0001.sig>