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
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