Bug 766579 - Part 2: Intertwine during sampling. r=jmuizelaar

--HG--
extra : rebase_source : e2ddcc188fcd6a2b3b6c35d3517fb7ec8ae7deab

tools/profiler/TableTicker.cpp

@@ -561,6 +561,33 @@ JSObject* TableTicker::ToJSObject(JSContext *aCx)
   return profile;
 }
 
+static
+void addProfileEntry(ProfileStack *aStack, ThreadProfile &aProfile, int i)
+{
+  // First entry has tagName 's' (start)
+  // Check for magic pointer bit 1 to indicate copy
+  const char* sampleLabel = aStack->mStack[i].mLabel;
+  if (aStack->mStack[i].isCopyLabel()) {
+    // Store the string using 1 or more 'd' (dynamic) tags
+    // that will happen to the preceding tag
+
+    aProfile.addTag(ProfileEntry('c', ""));
+    // Add one to store the null termination
+    size_t strLen = strlen(sampleLabel) + 1;
+    for (size_t j = 0; j < strLen;) {
+      // Store as many characters in the void* as the platform allows
+      char text[sizeof(void*)];
+      for (size_t pos = 0; pos < sizeof(void*) && j+pos < strLen; pos++) {
+        text[pos] = sampleLabel[j+pos];
+      }
+      j += sizeof(void*)/sizeof(char);
+      // Cast to *((void**) to pass the text data to a void*
+      aProfile.addTag(ProfileEntry('d', *((void**)(&text[0]))));
+    }
+  } else {
+    aProfile.addTag(ProfileEntry('c', sampleLabel));
+  }
+}
 
 #ifdef USE_BACKTRACE
 void TableTicker::doBacktrace(ThreadProfile &aProfile, TickSample* aSample)
@@ -581,6 +608,7 @@ void TableTicker::doBacktrace(ThreadProfile &aProfile, TickSample* aSample)
 #ifdef USE_NS_STACKWALK
 typedef struct {
   void** array;
+  void** sp_array;
   size_t size;
   size_t count;
 } PCArray;
@@ -593,7 +621,9 @@ void StackWalkCallback(void* aPC, void* aSP, void* aClosure)
     // too many frames, ignore
     return;
   }
-  array->array[array->count++] = aPC;
+  array->sp_array[array->count] = aSP;
+  array->array[array->count] = aPC;
+  array->count++;
 }
 
 void TableTicker::doBacktrace(ThreadProfile &aProfile, TickSample* aSample)
@@ -603,8 +633,10 @@ void TableTicker::doBacktrace(ThreadProfile &aProfile, TickSample* aSample)
   MOZ_ASSERT(thread);
 #endif
   void* pc_array[1000];
+  void* sp_array[1000];
   PCArray array = {
     pc_array,
+    sp_array,
     mozilla::ArrayLength(pc_array),
     0
   };
@@ -624,8 +656,39 @@ void TableTicker::doBacktrace(ThreadProfile &aProfile, TickSample* aSample)
   if (NS_SUCCEEDED(rv)) {
     aProfile.addTag(ProfileEntry('s', "(root)"));
 
+    ProfileStack* stack = aProfile.GetStack();
+    int pseudoStackPos = 0;
+
+    /* We have two stacks, the native C stack we extracted from unwinding,
+     * and the pseudostack we managed during execution. We want to consolidate
+     * the two in order. We do so by merging using the approximate stack address
+     * when each entry was push. When pushing JS entry we may not now the stack
+     * address in which case we have a NULL stack address in which case we assume
+     * that it follows immediatly the previous element.
+     *
+     *  C Stack | Address    --  Pseudo Stack | Address
+     *  main()  | 0x100          run_js()     | 0x40
+     *  start() | 0x80           jsCanvas()   | NULL
+     *  timer() | 0x50           drawLine()   | NULL
+     *  azure() | 0x10
+     *
+     * Merged: main(), start(), timer(), run_js(), jsCanvas(), drawLine(), azure()
+     */
+    // i is the index in C stack starting at main and decreasing
+    // pseudoStackPos is the position in the Pseudo stack starting
+    // at the first frame (run_js in the example) and increasing.
     for (size_t i = array.count; i > 0; --i) {
-      aProfile.addTag(ProfileEntry('l', (void*)array.array[i - 1]));
+      while (pseudoStackPos < stack->mStackPointer) {
+        volatile StackEntry& entry = stack->mStack[pseudoStackPos];
+
+        if (entry.mStackAddress < array.sp_array[i-1] && entry.mStackAddress)
+          break;
+
+        addProfileEntry(stack, aProfile, pseudoStackPos);
+        pseudoStackPos++;
+      }
+
+      aProfile.addTag(ProfileEntry('l', (void*)array.array[i-1]));
     }
   }
 }
@@ -689,29 +752,7 @@ void doSampleStackTrace(ProfileStack *aStack, ThreadProfile &aProfile, TickSampl
   for (mozilla::sig_safe_t i = 0;
        i < aStack->mStackPointer && i < mozilla::ArrayLength(aStack->mStack);
        i++) {
-    // First entry has tagName 's' (start)
-    // Check for magic pointer bit 1 to indicate copy
-    const char* sampleLabel = aStack->mStack[i].mLabel;
-    if (aStack->mStack[i].isCopyLabel()) {
-      // Store the string using 1 or more 'd' (dynamic) tags
-      // that will happen to the preceding tag
-
-      aProfile.addTag(ProfileEntry('c', ""));
-      // Add one to store the null termination
-      size_t strLen = strlen(sampleLabel) + 1;
-      for (size_t j = 0; j < strLen;) {
-        // Store as many characters in the void* as the platform allows
-        char text[sizeof(void*)];
-        for (size_t pos = 0; pos < sizeof(void*) && j+pos < strLen; pos++) {
-          text[pos] = sampleLabel[j+pos];
-        }
-        j += sizeof(void*);
-        // Take '*((void**)(&text[0]))' to pass the char[] as a single void*
-        aProfile.addTag(ProfileEntry('d', *((void**)(&text[0]))));
-      }
-    } else {
-      aProfile.addTag(ProfileEntry('c', sampleLabel));
-    }
+    addProfileEntry(aStack, aProfile, i);
   }
 #ifdef ENABLE_SPS_LEAF_DATA
   if (sample) {

tools/profiler/sampler.h

@@ -44,7 +44,6 @@
  *          application is responding to the event loop. Lower is better.
  * 't' - Elapse time since recording started.
  *
- * NOTE: File format is planned to be extended to include a dictionary to reduce size.
  */
 
 #ifndef SAMPLER_H

tools/profiler/sps_sampler.h

@@ -155,7 +155,7 @@ class NS_STACK_CLASS SamplerStackFrameRAII {
 public:
   // we only copy the strings at save time, so to take multiple parameters we'd need to copy them then.
   SamplerStackFrameRAII(const char *aInfo) {
-    mHandle = mozilla_sampler_call_enter(aInfo);
+    mHandle = mozilla_sampler_call_enter(aInfo, this, false);
   }
   ~SamplerStackFrameRAII() {
     mozilla_sampler_call_exit(mHandle);