The patch provides support for quantifying the cost of micro level operations on arm64 hardware. The supported operations include hypercall, mmio accesses, EOI virtual interrupt, and IPI send. Measurements are currently obtained using timer counters. Further modifications in KVM will be required to support timestamping using cycle counters, as KVM now disables accesses to the PMU counters from the VM. We iterate each of the tests for millions of times and output their average, minimum and maximum cost in timer counts. Instruction barriers were used before and after taking timestamps to avoid out-of-order execution or pipelining from skewing our measurements. To improve precision in the measurements, one should consider pinning each VCPU to a specific physical CPU (PCPU) and ensure no other task could run on that PCPU to skew the results. This can be achieved by enabling QMP server in the QEMU command in unittest.cfg for micro test, allowing a client program to get the thread_id for each VCPU thread from the QMP server. Based on the information, the client program can then pin the corresponding VCPUs to dedicated PCPUs and isolate interrupts and tasks from those PCPUs. The patch has been tested on arm64 hardware including AMD Seattle and ThunderX2, which has GICv2 and GICv3 respectively. Shih-Wei Li (1): arm64: add micro test arm/Makefile.common | 1 + arm/micro-test.c | 289 ++++++++++++++++++++++++++++++++++++++++++++++++++++ arm/unittests.cfg | 6 ++ 3 files changed, 296 insertions(+) create mode 100644 arm/micro-test.c -- 1.9.1
