Module: Sperf::PProf

Defined in:
lib/sperf.rb

Overview

Hand-written protobuf encoder for pprof profile format. Only runs once at stop time, so performance is not critical.

Samples from C are: [[[path_str, label_str], …], weight] This encoder builds its own string table for pprof output.

Class Method Summary collapse

Class Method Details

.build_tables(merged) ⇒ Object 



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# File 'lib/sperf.rb', line 533

def build_tables(merged)
  locations = {}
  functions = {}
  next_id = 1

  merged.each do |frames, _weight|
    frames.each do |frame|
      unless locations.key?(frame)
        locations[frame] = next_id
        functions[frame] = next_id
        next_id += 1
      end
    end
  end

  [locations, functions]
end

.encode(data) ⇒ Object 



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# File 'lib/sperf.rb', line 450

def encode(data)
  samples_raw = data[:samples]
  frequency = data[:frequency]
  interval_ns = 1_000_000_000 / frequency
  mode = data[:mode] || :cpu

  # Build string table: index 0 must be ""
  string_table = [""]
  string_index = { "" => 0 }

  intern = ->(s) {
    string_index[s] ||= begin
      idx = string_table.size
      string_table << s
      idx
    end
  }

  # Convert string frames to index frames and merge identical stacks
  merged = Hash.new(0)
  samples_raw.each do |frames, weight|
    key = frames.map { |path, label| [intern.(path), intern.(label)] }
    merged[key] += weight
  end
  merged = merged.to_a

  # Build location/function tables
  locations, functions = build_tables(merged)

  # Intern type label and unit
  type_label = mode == :wall ? "wall" : "cpu"
  type_idx = intern.(type_label)
  ns_idx = intern.("nanoseconds")

  # Encode Profile message
  buf = "".b

  # field 1: sample_type (repeated ValueType)
  buf << encode_message(1, encode_value_type(type_idx, ns_idx))

  # field 2: sample (repeated Sample)
  merged.each do |frames, weight|
    sample_buf = "".b
    loc_ids = frames.map { |f| locations[f] }
    sample_buf << encode_packed_uint64(1, loc_ids)
    sample_buf << encode_packed_int64(2, [weight])
    buf << encode_message(2, sample_buf)
  end

  # field 4: location (repeated Location)
  locations.each do |frame, loc_id|
    loc_buf = "".b
    loc_buf << encode_uint64(1, loc_id)
    line_buf = "".b
    func_id = functions[frame]
    line_buf << encode_uint64(1, func_id)
    loc_buf << encode_message(4, line_buf)
    buf << encode_message(4, loc_buf)
  end

  # field 5: function (repeated Function)
  functions.each do |frame, func_id|
    func_buf = "".b
    func_buf << encode_uint64(1, func_id)
    func_buf << encode_int64(2, frame[1])    # name (label_idx)
    func_buf << encode_int64(4, frame[0])    # filename (path_idx)
    buf << encode_message(5, func_buf)
  end

  # field 6: string_table (repeated string)
  string_table.each do |s|
    buf << encode_bytes(6, s.encode("UTF-8"))
  end

  # field 11: period_type (ValueType)
  buf << encode_message(11, encode_value_type(type_idx, ns_idx))

  # field 12: period (int64)
  buf << encode_int64(12, interval_ns)

  buf
end

.encode_bytes(field, data) ⇒ Object 



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# File 'lib/sperf.rb', line 577

def encode_bytes(field, data)
  data = data.b if data.respond_to?(:b)
  encode_varint((field << 3) | 2) + encode_varint(data.bytesize) + data
end

.encode_int64(field, value) ⇒ Object 



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# File 'lib/sperf.rb', line 573

def encode_int64(field, value)
  encode_varint((field << 3) | 0) + encode_varint(value < 0 ? value + (1 << 64) : value)
end

.encode_message(field, data) ⇒ Object 



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# File 'lib/sperf.rb', line 582

def encode_message(field, data)
  encode_bytes(field, data)
end

.encode_packed_int64(field, values) ⇒ Object 



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# File 'lib/sperf.rb', line 595

def encode_packed_int64(field, values)
  inner = values.map { |v| encode_varint(v < 0 ? v + (1 << 64) : v) }.join
  encode_bytes(field, inner)
end

.encode_packed_uint64(field, values) ⇒ Object 



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# File 'lib/sperf.rb', line 590

def encode_packed_uint64(field, values)
  inner = values.map { |v| encode_varint(v) }.join
  encode_bytes(field, inner)
end

.encode_uint64(field, value) ⇒ Object 



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# File 'lib/sperf.rb', line 569

def encode_uint64(field, value)
  encode_varint((field << 3) | 0) + encode_varint(value)
end

.encode_value_type(type_idx, unit_idx) ⇒ Object 



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# File 'lib/sperf.rb', line 586

def encode_value_type(type_idx, unit_idx)
  encode_int64(1, type_idx) + encode_int64(2, unit_idx)
end

.encode_varint(value) ⇒ Object

— Protobuf encoding helpers —



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# File 'lib/sperf.rb', line 553

def encode_varint(value)
  value = value & 0xFFFFFFFF_FFFFFFFF if value < 0
  buf = "".b
  loop do
    byte = value & 0x7F
    value >>= 7
    if value > 0
      buf << (byte | 0x80).chr
    else
      buf << byte.chr
      break
    end
  end
  buf
end