factor/vm/sampling_profiler.cpp

#include "master.hpp"

namespace factor {

profiling_sample_count profiling_sample_count::record_counts() volatile {
  atomic::fence();
  profiling_sample_count returned(sample_count, gc_sample_count,
                                  jit_sample_count, foreign_sample_count,
                                  foreign_thread_sample_count);
  atomic::fetch_subtract(&sample_count, returned.sample_count);
  atomic::fetch_subtract(&gc_sample_count, returned.gc_sample_count);
  atomic::fetch_subtract(&jit_sample_count, returned.jit_sample_count);
  atomic::fetch_subtract(&foreign_sample_count, returned.foreign_sample_count);
  atomic::fetch_subtract(&foreign_thread_sample_count,
                         returned.foreign_thread_sample_count);
  return returned;
}

void profiling_sample_count::clear() volatile {
  sample_count = 0;
  gc_sample_count = 0;
  jit_sample_count = 0;
  foreign_sample_count = 0;
  foreign_thread_sample_count = 0;
  atomic::fence();
}

profiling_sample::profiling_sample(factor_vm* vm, bool prolog_p,
                                   profiling_sample_count const& counts,
                                   cell thread)
    : counts(counts), thread(thread) {
  vm->record_callstack_sample(&callstack_begin, &callstack_end, prolog_p);
}

void factor_vm::record_sample(bool prolog_p) {
  profiling_sample_count counts = safepoint.sample_counts.record_counts();
  if (!counts.empty())
    samples.push_back(profiling_sample(this, prolog_p, counts,
                                       special_objects[OBJ_CURRENT_THREAD]));
}

void factor_vm::record_callstack_sample(cell* begin, cell* end, bool prolog_p) {
  *begin = sample_callstacks.size();

  bool skip_p = prolog_p;
  auto recorder = [&](cell frame_top, cell size, code_block* owner, cell addr) {
    if (skip_p)
      skip_p = false;
    else
      sample_callstacks.push_back(owner->owner);
  };
  iterate_callstack(ctx, recorder);

  *end = sample_callstacks.size();

  std::reverse(sample_callstacks.begin() + *begin, sample_callstacks.end());
}

void factor_vm::set_sampling_profiler(fixnum rate) {
  bool sampling_p = !!rate;
  if (sampling_p == !!atomic::load(&sampling_profiler_p))
    return;

  if (sampling_p)
    start_sampling_profiler(rate);
  else
    end_sampling_profiler();
}

void factor_vm::clear_samples() {
  // Swapping into temporaries releases the vector's allocated storage,
  // whereas clear() would leave the allocation as-is
  std::vector<profiling_sample> sample_graveyard;
  std::vector<cell> sample_callstack_graveyard;
  samples.swap(sample_graveyard);
  sample_callstacks.swap(sample_callstack_graveyard);
}

void factor_vm::start_sampling_profiler(fixnum rate) {
  samples_per_second = rate;
  safepoint.sample_counts.clear();
  clear_samples();
  samples.reserve(10 * rate);
  sample_callstacks.reserve(100 * rate);
  atomic::store(&sampling_profiler_p, true);
  start_sampling_profiler_timer();
}

void factor_vm::end_sampling_profiler() {
  atomic::store(&sampling_profiler_p, false);
  end_sampling_profiler_timer();
  record_sample(false);
}

void factor_vm::primitive_sampling_profiler() {
  set_sampling_profiler(to_fixnum(ctx->pop()));
}

/* Allocates memory */
void factor_vm::primitive_get_samples() {
  if (atomic::load(&sampling_profiler_p) || samples.empty()) {
    ctx->push(false_object);
  } else {
    data_root<array> samples_array(allot_array(samples.size(), false_object),
                                   this);
    std::vector<profiling_sample>::const_iterator from_iter = samples.begin();
    cell to_i = 0;

    for (; from_iter != samples.end(); ++from_iter, ++to_i) {
      data_root<array> sample(allot_array(7, false_object), this);

      set_array_nth(sample.untagged(), 0,
                    tag_fixnum(from_iter->counts.sample_count));
      set_array_nth(sample.untagged(), 1,
                    tag_fixnum(from_iter->counts.gc_sample_count));
      set_array_nth(sample.untagged(), 2,
                    tag_fixnum(from_iter->counts.jit_sample_count));
      set_array_nth(sample.untagged(), 3,
                    tag_fixnum(from_iter->counts.foreign_sample_count));
      set_array_nth(sample.untagged(), 4,
                    tag_fixnum(from_iter->counts.foreign_thread_sample_count));

      set_array_nth(sample.untagged(), 5, from_iter->thread);

      cell callstack_size =
          from_iter->callstack_end - from_iter->callstack_begin;
      data_root<array> callstack(allot_array(callstack_size, false_object),
                                 this);

      std::vector<cell>::const_iterator callstacks_begin =
                                            sample_callstacks.begin(),
                                        c_from_iter =
                                            callstacks_begin +
                                            from_iter->callstack_begin,
                                        c_from_iter_end =
                                            callstacks_begin +
                                            from_iter->callstack_end;
      cell c_to_i = 0;

      for (; c_from_iter != c_from_iter_end; ++c_from_iter, ++c_to_i)
        set_array_nth(callstack.untagged(), c_to_i, *c_from_iter);

      set_array_nth(sample.untagged(), 6, callstack.value());

      set_array_nth(samples_array.untagged(), to_i, sample.value());
    }
    ctx->push(samples_array.value());
  }
}

void factor_vm::primitive_clear_samples() { clear_samples(); }

}