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 */
};
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 */
};
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).
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
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