Profiler

[swatanabe-b1]

Running the profiler

The profiler only works with specific template parameters backend<..., jit_profile, ..., profile_instr_map>. jit_profile allows capturing stack traces, profile_instr_map allows mapping host code addresses to offsets in the wasm file.

The profiler can be executed by creating a scoped_profile object around wasm execution. Multiple profiler instances are supported, but a single thread can only run one at a time.

profile_data pd("file name", bkend); // stores profiling information and writes it to a file
...
{
  scoped_profile start(&pd); // start the profiler
  bkend.call();
}

The profiler's sampling rate can be set by calling set_profile_interval_us before starting the profiler. The default is 10 ms.

eos-vm-interp has an extra -p option, which enables profiling.

Interpreting the output

The output is generated in the format used by gperftools. It can be processed by pprof with the help of a custom addr2line implementation. eos-vm-addr2line can only determine the function names. It does not yet know how to parse DWARF, so it cannot provide source line numbers.

Example Usage

eos-vm-interp -p profilee.wasm
pprof --tools=addr2line:path/to/eos-vm/tools/eos-vm-addr2line,objdump:objdump,c++filt:c++filt,nm:nm --collapsed profilee.wasm profile.out > profile.collapsed
flamegraph.pl profile.collapsed > profile.svg