Pack stack traces in pprof format

async-profiler · Mar 26, 2024 · 978fe2c · 978fe2c
1 parent 5da0a5f
commit 978fe2c
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Showing 2 changed files with 22 additions and 2 deletions.
diff --git a/src/converter/one/convert/JfrToPprof.java b/src/converter/one/convert/JfrToPprof.java
@@ -81,10 +81,12 @@ public void dump(OutputStream out) throws IOException {
     }
 
     private Proto sample(Proto s, Event event, long value) {
+        int packedLocations = s.startField(1);
+
         long classId = event.classId();
         if (classId != 0) {
             int function = functions.index(getClassName(classId));
-            s.field(1, locations.index((long) function << 16));
+            s.writeInt(locations.index((long) function << 16));
         }
 
         StackTrace stackTrace = jfr.stackTraces.get(event.stackTraceId);
@@ -95,10 +97,11 @@ private Proto sample(Proto s, Event event, long value) {
             for (int i = 0; i < methods.length; i++) {
                 String methodName = getMethodName(methods[i], types[i]);
                 int function = functions.index(methodName);
-                s.field(1, locations.index((long) function << 16 | lines[i] >>> 16));
+                s.writeInt(locations.index((long) function << 16 | lines[i] >>> 16));
             }
         }
 
+        s.commitField(packedLocations);
         s.field(2, value);
 
         if (args.threads && event.tid != 0) {

diff --git a/src/converter/one/proto/Proto.java b/src/converter/one/proto/Proto.java
@@ -69,6 +69,23 @@ public Proto field(int index, Proto proto) {
         return this;
     }
 
+    public int startField(int index) {
+        tag(index, 2);
+        ensureCapacity(3);
+        return pos += 3;
+    }
+
+    public void commitField(int mark) {
+        int length = pos - mark;
+        if (length >= 1 << (7 * 3)) {
+            throw new IllegalArgumentException("Field too large");
+        }
+
+        buf[mark - 3] = (byte) (0x80 | (length & 0x7f));
+        buf[mark - 2] = (byte) (0x80 | ((length >>> 7) & 0x7f));
+        buf[mark - 1] = (byte) (length >>> 14);
+    }
+
     public void writeInt(int n) {
         int length = n == 0 ? 1 : (38 - Integer.numberOfLeadingZeros(n)) / 7;
         ensureCapacity(length);