Added the simplest call stack sampling and call profile in tick processor output.

Currently only two stack frames are sampled (current function and its caller).

Output of tick processor looks like this:

 [Call profile]:
   total  call path
   15.2%  LazyCompile: am3 crypto.js:108  <-  LazyCompile: montReduce crypto.js:583
    6.5%  LazyCompile: am3 crypto.js:108  <-  LazyCompile: bnpSquareTo crypto.js:431
    2.9%  Builtin: KeyedStoreIC_Generic  <-  LazyCompile: montReduce crypto.js:583
    2.3%  LazyCompile: am3 crypto.js:108  <-  LazyCompile: bnpMultiplyTo crypto.js:415

Tested under Windows, Linux and OS X.

Review URL: http://codereview.chromium.org/21403


git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@1292 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/log.cc

@@ -139,12 +139,14 @@ bool Profiler::paused_ = false;
 //
 class Ticker: public Sampler {
  public:
-  explicit Ticker(int interval):
-      Sampler(interval, FLAG_prof), window_(NULL), profiler_(NULL) {}
+  explicit Ticker(int interval, unsigned int low_stack_bound):
+      Sampler(interval, FLAG_prof), window_(NULL), profiler_(NULL),
+      low_stack_bound_(low_stack_bound) {}
 
   ~Ticker() { if (IsActive()) Stop(); }
 
   void Tick(TickSample* sample) {
+    if (IsProfiling()) SampleStack(sample);
     if (profiler_) profiler_->Insert(sample);
     if (window_) window_->AddState(sample->state);
   }
@@ -170,8 +172,21 @@ class Ticker: public Sampler {
   }
 
  private:
+  void SampleStack(TickSample* sample) {
+    // Assuming that stack grows from lower addresses
+    if (sample->sp < sample->fp && sample->fp < low_stack_bound_) {
+      sample->InitStack(1);
+      sample->stack[0] = Memory::Address_at(
+          (Address)(sample->fp + StandardFrameConstants::kCallerPCOffset));
+    } else {
+      // FP seems to be in some intermediate state, better discard this sample
+      sample->InitStack(0);
+    }
+  }
+
   SlidingStateWindow* window_;
   Profiler* profiler_;
+  unsigned int low_stack_bound_;
 };
 
 
@@ -239,9 +254,6 @@ void Profiler::Disengage() {
   // the thread to terminate.
   running_ = false;
   TickSample sample;
-  sample.pc = 0;
-  sample.sp = 0;
-  sample.state = OTHER;
   Insert(&sample);
   Join();
 
@@ -900,6 +912,11 @@ void Logger::TickEvent(TickSample* sample, bool overflow) {
   if (overflow) {
     msg.Append(",overflow");
   }
+  if (*(sample->stack)) {
+    for (size_t i = 0; sample->stack[i]; ++i) {
+      msg.Append(",0x%x", reinterpret_cast<unsigned int>(sample->stack[i]));
+    }
+  }
   msg.Append('\n');
   msg.WriteToLogFile();
 }
@@ -990,7 +1007,10 @@ bool Logger::Setup() {
 
   current_state_ = new VMState(OTHER);
 
-  ticker_ = new Ticker(10);
+  // as log is initialized early with V8, we can assume that JS execution
+  // frames can never reach this point on stack
+  int stack_var;
+  ticker_ = new Ticker(10, reinterpret_cast<unsigned int>(&stack_var));
 
   if (FLAG_sliding_state_window && sliding_state_window_ == NULL) {
     sliding_state_window_ = new SlidingStateWindow();

src/platform-freebsd.cc

@@ -634,9 +634,11 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 #if defined (__arm__) || defined(__thumb__)
     sample.pc = mcontext.mc_r15;
     sample.sp = mcontext.mc_r13;
+    sample.fp = mcontext.mc_r11;
 #else
     sample.pc = mcontext.mc_eip;
     sample.sp = mcontext.mc_esp;
+    sample.fp = mcontext.mc_ebp;
 #endif
   }
 

src/platform-linux.cc

@@ -617,9 +617,11 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 #if defined (__arm__) || defined(__thumb__)
     sample.pc = mcontext.gregs[R15];
     sample.sp = mcontext.gregs[R13];
+    sample.fp = mcontext.gregs[R11];
 #else
     sample.pc = mcontext.gregs[REG_EIP];
     sample.sp = mcontext.gregs[REG_ESP];
+    sample.fp = mcontext.gregs[REG_EBP];
 #endif
   }
 

src/platform-macos.cc

@@ -583,9 +583,11 @@ static void ProfilerSignalHandler(int signal, siginfo_t* info, void* context) {
 #if __DARWIN_UNIX03
     sample.pc = mcontext->__ss.__eip;
     sample.sp = mcontext->__ss.__esp;
+    sample.fp = mcontext->__ss.__ebp;
 #else  // !__DARWIN_UNIX03
     sample.pc = mcontext->ss.eip;
     sample.sp = mcontext->ss.esp;
+    sample.fp = mcontext->ss.ebp;
 #endif  // __DARWIN_UNIX03
   }
 

src/platform-win32.cc

@@ -1585,6 +1585,7 @@ class Sampler::PlatformData : public Malloced {
         // Invoke tick handler with program counter and stack pointer.
         sample.pc = context.Eip;
         sample.sp = context.Esp;
+        sample.fp = context.Ebp;
       }
 
       // We always sample the VM state.

src/platform.h

@@ -422,10 +422,29 @@ class Semaphore {
 // TickSample captures the information collected for each sample.
 class TickSample {
  public:
-  TickSample() : pc(0), sp(0), state(OTHER) {}
+  TickSample() : pc(0), sp(0), fp(0), state(OTHER) {}
   unsigned int pc;  // Instruction pointer.
   unsigned int sp;  // Stack pointer.
+  unsigned int fp;  // Frame pointer.
   StateTag state;   // The state of the VM.
+  SmartPointer<Address> stack;  // Call stack, null-terminated.
+
+  inline TickSample& operator=(const TickSample& rhs) {
+    if (this == &rhs) return *this;
+    pc = rhs.pc;
+    sp = rhs.sp;
+    fp = rhs.fp;
+    state = rhs.state;
+    DeleteArray(stack.Detach());
+    stack = rhs.stack;
+    return *this;
+  }
+
+  inline void InitStack(int depth) {
+    stack = SmartPointer<Address>(NewArray<Address>(depth + 1));
+    // null-terminate
+    stack[depth] = 0;
+  }
 };
 
 class Sampler {

tools/tickprocessor.py

@@ -26,6 +26,7 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 import csv, splaytree, sys
+from operator import itemgetter
 
 
 class CodeEntry(object):
@@ -34,9 +35,14 @@ class CodeEntry(object):
     self.start_addr = start_addr
     self.tick_count = 0
     self.name = name
+    self.stacks = {}
 
-  def Tick(self, pc):
+  def Tick(self, pc, stack):
     self.tick_count += 1
+    if len(stack) > 0:
+      stack.insert(0, self.ToString())
+      stack_key = tuple(stack)
+      self.stacks[stack_key] = self.stacks.setdefault(stack_key, 0) + 1
 
   def RegionTicks(self):
     return None
@@ -69,8 +75,8 @@ class JSCodeEntry(CodeEntry):
     self.assembler = assembler
     self.region_ticks = None
 
-  def Tick(self, pc):
-    super(JSCodeEntry, self).Tick(pc)
+  def Tick(self, pc, stack):
+    super(JSCodeEntry, self).Tick(pc, stack)
     if not pc is None:
       offset = pc - self.start_addr
       seen = []
@@ -162,7 +168,7 @@ class TickProcessor(object):
       logreader = csv.reader(logfile)
       for row in logreader:
         if row[0] == 'tick':
-          self.ProcessTick(int(row[1], 16), int(row[2], 16), int(row[3]))
+          self.ProcessTick(int(row[1], 16), int(row[2], 16), int(row[3]), row[4:])
         elif row[0] == 'code-creation':
           self.ProcessCodeCreation(row[1], int(row[2], 16), int(row[3]), row[4])
         elif row[0] == 'code-move':
@@ -237,25 +243,41 @@ class TickProcessor(object):
   def IncludeTick(self, pc, sp, state):
     return (self.included_state is None) or (self.included_state == state)
 
-  def ProcessTick(self, pc, sp, state):
-    if not self.IncludeTick(pc, sp, state):
-      self.excluded_number_of_ticks += 1;
-      return
-    self.total_number_of_ticks += 1
+  def FindEntry(self, pc):
     page = pc >> 12
     if page in self.vm_extent:
-      entry = self.cpp_entries.FindGreatestsLessThan(pc).value
-      if entry.IsSharedLibraryEntry():
-        self.number_of_library_ticks += 1
-      entry.Tick(None)
-      return
+      entry = self.cpp_entries.FindGreatestsLessThan(pc)
+      if entry != None:
+        return entry.value
+      else:
+        return entry
     max = self.js_entries.FindMax()
     min = self.js_entries.FindMin()
     if max != None and pc < max.key and pc > min.key:
-      code_obj = self.js_entries.FindGreatestsLessThan(pc).value
-      code_obj.Tick(pc)
+      return self.js_entries.FindGreatestsLessThan(pc).value
+    return None
+
+  def ProcessStack(self, stack):
+    result = []
+    for frame in stack:
+      if frame.startswith('0x'):
+        entry = self.FindEntry(int(frame, 16))
+        if entry != None:
+          result.append(entry.ToString())
+    return result
+
+  def ProcessTick(self, pc, sp, state, stack):
+    if not self.IncludeTick(pc, sp, state):
+      self.excluded_number_of_ticks += 1;
       return
-    self.unaccounted_number_of_ticks += 1
+    self.total_number_of_ticks += 1
+    entry = self.FindEntry(pc)
+    if entry == None:
+      self.unaccounted_number_of_ticks += 1
+      return
+    if entry.IsSharedLibraryEntry():
+      self.number_of_library_ticks += 1
+    entry.Tick(pc, self.ProcessStack(stack))
 
   def PrintResults(self):
     print('Statistical profiling result from %s, (%d ticks, %d unaccounted, %d excluded).' %
@@ -276,6 +298,11 @@ class TickProcessor(object):
       # Print the C++ ticks.
       self.PrintHeader('C++')
       self.PrintEntries(cpp_entries, lambda e:not e.IsSharedLibraryEntry())
+      # Print call profile.
+      print('\n [Call profile]:')
+      print('   total  call path')
+      js_entries.extend(cpp_entries)
+      self.PrintCallProfile(js_entries)
 
   def PrintHeader(self, header_title):
     print('\n [%s]:' % header_title)
@@ -309,5 +336,21 @@ class TickProcessor(object):
               'name': name
             })
 
+  def PrintCallProfile(self, entries):
+    all_stacks = {}
+    total_stacks = 0
+    for entry in entries:
+      all_stacks.update(entry.stacks)
+      for count in entry.stacks.itervalues():
+        total_stacks += count
+    all_stacks_items = all_stacks.items();
+    all_stacks_items.sort(key = itemgetter(1), reverse=True)
+    for stack, count in all_stacks_items:
+      total_percentage = count * 100.0 / total_stacks
+      print('  %(total)5.1f%%  %(call_path)s' % {
+        'total' : total_percentage,
+        'call_path' : stack[0] + '  <-  ' + stack[1]
+      })
+
 if __name__ == '__main__':
   sys.exit('You probably want to run windows-tick-processor.py or linux-tick-processor.py.')