ray1129 / riscv-hpmcounters

A simple utility for doing RISC-V HPM perf monitoring.

About

This utility helps monitor performance of RISC-V processors running Linux.

RISC-V processors implement Hardware Performance Monitor (HPM) counters.

So long as these counters are unprotected and not saved and restored on context switches, Process A can read the HPM counters to monitor the performance of Process B.

hpm_counters is a binary that can run in Linux and checkpoint the HPM counters every (roughly) 100M cycles (you can set the sleep time). When hpm_counters is sent a SIGKILL, it will print out all of its checkpoints.

Requirements

You must install the glibc/Linux RISC-V gcc cross compiler (riscv64-unknown-linux-gnu-g++).

You must modify the machine initialization in your boot process to initialize the HPM counters are desired. You must also give user-access privileges to the HPM counters:

// For the Berkeley Boot Loader, riscv-tools/riscv-pk/machine/minit.c
static void mstatus_init()                                   
{                                                            
  ...                             
  // Enable user/supervisor use of perf counters             
  write_csr(mucounteren, -1);                                
  write_csr(mscounteren, -1);   
  
  // Set the HPM event selectors as desired for your specific micro-architecture
  write_csr(mhpmevent3, 1)
  write_csr(mhpmevent4, 2)
  write_csr(mhpmevent5, 3)
  ...
}

How to Use?

    $ ./hpm_counters &
    $ ./mybenchmark
    $ killall hpm_counters
    $ while pgrep hpm_counters > /dev/null; do sleep 1; done