I am using perf for checking the cache performance I am using the following command in ubuntu but it does not give the required output. I want to check cache references and cache-misses. this command is working on core i5 but it does not work on the virtual machine.
$ perf stat -r 5 -B perf stat -r 5 -B -e cache-references,cache-misses, ./cmiss
the output of the above command on virtual machine is:
Performance counter stats for './cmiss' (5 runs):
cache-references
cache-misses
66.994228 cpu-clock ( +- 0.14% )
0.067178350 seconds time elapsed ( +- 0.13% )
The data you want is in hardware based Performance Monitoring Counters. These are typically NOT emulated by virtual machine environments because they are overhead and generally meaningless given the underlying caching statistics are maintained on a per core / package basis and the workload can be scheduled to run on a variety of cores, each with its own hardware level statistics.
Some virtualization technologies can emulate these counters. It does so by taking a picture of the actual hardware counters on the cores currently running the workload. Then when the workload is task switched off the core, the delta in the underlying physical counters is computed and applied to a virtual counter. Since the underlyign time base is also virtual, computing pages fault per second, for example, is meaningless as you have no way to know if the workload was scheduled for a 100% duty cycle or 1%. e.g. the meaning of 100 faults per "second" varies greatly depending on how much actual compute time the workload had available.
As mentioned by Peter, this housekeeping and also the diminished meaning / significance to the statistics makes it a futile effort in most cases.
You can, for example, in VMWARE ESX, enable PMC - with a lot of caveats. Specifically it complicates live move comparability, as the guests cannot be migrated to a host with even seemingly trivial differences in PMC capabilities. In EVC, where the guests are lied to, making all hosts seems like a lowest common denominator processor model / stepping, you cannot enable the counters because they cannot be reliably masked - the guest OS may still discover the counters are available on boot, then once the guest is migrated, an invalid opcode will be thrown on access.
So.... short answer: no. long answer: yes, with animal sacrifices.
-- Bob
http://stackoverflow.com/questions/14674463/why-doesnt-perf-report-cache-misses
https://software.intel.com/en-us/forums/intel-performance-tuning-utility/topic/288159
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