8351594: JFR: Rate-limited sampling of Java events

src/java.base/share/classes/java/io/FileInputStream.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1994, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -205,22 +205,17 @@ public int read() throws IOException {
 
     private int traceRead0() throws IOException {
         int result = 0;
-        boolean endOfFile = false;
         long bytesRead = 0;
-        long start = 0;
+        long start = FileReadEvent.timestamp();
         try {
-            start = FileReadEvent.timestamp();
             result = read0();
             if (result < 0) {
-                endOfFile = true;
+                bytesRead = -1;
             } else {
                 bytesRead = 1;
             }
         } finally {
-            long duration = FileReadEvent.timestamp() - start;
-            if (FileReadEvent.shouldCommit(duration)) {
-                FileReadEvent.commit(start, duration, path, bytesRead, endOfFile);
-            }
+            FileReadEvent.offer(start, path, bytesRead);
         }
         return result;
     }
@@ -236,19 +231,11 @@ private int traceRead0() throws IOException {
 
     private int traceReadBytes(byte b[], int off, int len) throws IOException {
         int bytesRead = 0;
-        long start = 0;
+        long start = FileReadEvent.timestamp();
         try {
-            start = FileReadEvent.timestamp();
             bytesRead = readBytes(b, off, len);
         } finally {
-            long duration = FileReadEvent.timestamp() - start;
-            if (FileReadEvent.shouldCommit(duration)) {
-                if (bytesRead < 0) {
-                    FileReadEvent.commit(start, duration, path, 0L, true);
-                } else {
-                    FileReadEvent.commit(start, duration, path, bytesRead, false);
-                }
-            }
+            FileReadEvent.offer(start, path, bytesRead);
         }
         return bytesRead;
     }

src/java.base/share/classes/java/io/FileOutputStream.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1994, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -266,16 +266,12 @@ private void open(String name, boolean append) throws FileNotFoundException {
 
     private void traceWrite(int b, boolean append) throws IOException {
         long bytesWritten = 0;
-        long start = 0;
+        long start = FileWriteEvent.timestamp();
         try {
-            start = FileWriteEvent.timestamp();
             write(b, append);
             bytesWritten = 1;
         } finally {
-            long duration = FileWriteEvent.timestamp() - start;
-            if (FileWriteEvent.shouldCommit(duration)) {
-                FileWriteEvent.commit(start, duration, path, bytesWritten);
-            }
+            FileWriteEvent.offer(start, path, bytesWritten);
         }
     }
 
@@ -310,16 +306,12 @@ private native void writeBytes(byte[] b, int off, int len, boolean append)
 
     private void traceWriteBytes(byte b[], int off, int len, boolean append) throws IOException {
         long bytesWritten = 0;
-        long start = 0;
+        long start = FileWriteEvent.timestamp();
         try {
-            start = FileWriteEvent.timestamp();
             writeBytes(b, off, len, append);
             bytesWritten = len;
         } finally {
-            long duration = FileWriteEvent.timestamp() - start;
-            if (FileWriteEvent.shouldCommit(duration)) {
-                FileWriteEvent.commit(start, duration, path, bytesWritten);
-            }
+            FileWriteEvent.offer(start, path, bytesWritten);
         }
     }
 

src/java.base/share/classes/java/io/RandomAccessFile.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1994, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -367,21 +367,16 @@ public int read() throws IOException {
     private int traceRead0() throws IOException {
         int result = 0;
         long bytesRead = 0;
-        boolean endOfFile = false;
-        long start = 0;
+        long start = FileReadEvent.timestamp();
         try {
-            start = FileReadEvent.timestamp();
             result = read0();
             if (result < 0) {
-                endOfFile = true;
+                bytesRead = -1;
             } else {
                 bytesRead = 1;
             }
         } finally {
-            long duration = FileReadEvent.timestamp() - start;
-            if (FileReadEvent.shouldCommit(duration)) {
-                FileReadEvent.commit(start, duration, path, bytesRead, endOfFile);
-            }
+            FileReadEvent.offer(start, path, bytesRead);
         }
         return result;
     }
@@ -404,19 +399,11 @@ private int readBytes(byte[] b, int off, int len) throws IOException {
 
     private int traceReadBytes0(byte b[], int off, int len) throws IOException {
         int bytesRead = 0;
-        long start = 0;
+        long start = FileReadEvent.timestamp();
         try {
-            start = FileReadEvent.timestamp();
             bytesRead = readBytes0(b, off, len);
         } finally {
-            long duration = FileReadEvent.timestamp() - start;
-            if (FileReadEvent.shouldCommit(duration)) {
-                if (bytesRead < 0) {
-                    FileReadEvent.commit(start, duration, path, 0L, true);
-                } else {
-                    FileReadEvent.commit(start, duration, path, bytesRead, false);
-                }
-            }
+            FileReadEvent.offer(start, path, bytesRead);
         }
         return bytesRead;
     }
@@ -582,16 +569,12 @@ private void implWrite(int b) throws IOException {
 
     private void traceImplWrite(int b) throws IOException {
         long bytesWritten = 0;
-        long start = 0;
+        long start = FileWriteEvent.timestamp();
         try {
-            start = FileWriteEvent.timestamp();
             implWrite(b);
             bytesWritten = 1;
         } finally {
-            long duration = FileWriteEvent.timestamp() - start;
-            if (FileWriteEvent.shouldCommit(duration)) {
-                FileWriteEvent.commit(start, duration, path, bytesWritten);
-            }
+            FileWriteEvent.offer(start, path, bytesWritten);
         }
     }
 
@@ -624,16 +607,12 @@ private void implWriteBytes(byte[] b, int off, int len) throws IOException {
 
     private void traceImplWriteBytes(byte b[], int off, int len) throws IOException {
         long bytesWritten = 0;
-        long start = 0;
+        long start = FileWriteEvent.timestamp();
         try {
-            start = FileWriteEvent.timestamp();
             implWriteBytes(b, off, len);
             bytesWritten = len;
         } finally {
-            long duration = FileWriteEvent.timestamp() - start;
-            if (FileWriteEvent.shouldCommit(duration)) {
-                FileWriteEvent.commit(start, duration, path, bytesWritten);
-            }
+            FileWriteEvent.offer(start, path, bytesWritten);
         }
     }
 

src/java.base/share/classes/java/lang/Throwable.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1994, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1994, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -121,7 +121,7 @@ public class Throwable implements Serializable {
      * Flag set by jdk.internal.event.JFRTracing to indicate if
      * exceptions should be traced by JFR.
      */
-    static volatile boolean jfrTracing;
+    static boolean jfrTracing;
 
     /**
      * The JVM saves some indication of the stack backtrace in this slot.

src/java.base/share/classes/java/net/Socket.java

@@ -965,10 +965,7 @@ public int read(byte[] b, int off, int len) throws IOException {
             }
             long start = SocketReadEvent.timestamp();
             int nbytes = implRead(b, off, len);
-            long duration = SocketReadEvent.timestamp() - start;
-            if (SocketReadEvent.shouldCommit(duration)) {
-                SocketReadEvent.emit(start, duration, nbytes, parent.getRemoteSocketAddress(), getSoTimeout());
-            }
+            SocketReadEvent.offer(start, nbytes, parent.getRemoteSocketAddress(), getSoTimeout());
             return nbytes;
         }
 
@@ -1081,10 +1078,7 @@ public void write(byte[] b, int off, int len) throws IOException {
             }
             long start = SocketWriteEvent.timestamp();
             implWrite(b, off, len);
-            long duration = SocketWriteEvent.timestamp() - start;
-            if (SocketWriteEvent.shouldCommit(duration)) {
-                SocketWriteEvent.emit(start, duration, len, parent.getRemoteSocketAddress());
-            }
+            SocketWriteEvent.offer(start, len, parent.getRemoteSocketAddress());
         }
 
         private void implWrite(byte[] b, int off, int len) throws IOException {

src/java.base/share/classes/jdk/internal/event/ExceptionThrownEvent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -31,6 +31,11 @@ public final class ExceptionThrownEvent extends Event {
     public String message;
     public Class<?> thrownClass;
 
+    public static boolean shouldThrottleCommit(long timestamp) {
+        // Generated by JFR
+        return false;
+    }
+
     public static void commit(long start, String message, Class<?> thrownClass) {
         // Generated by JFR
     }

src/java.base/share/classes/jdk/internal/event/FileReadEvent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2024, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -45,11 +45,33 @@ public static long timestamp() {
         return 0L;
     }
 
-    public static boolean shouldCommit(long duration) {
+    public static boolean shouldThrottleCommit(long duration, long end) {
         // Generated by JFR
         return false;
     }
 
+    /**
+     * Helper method to offer the data needed to potentially commit an event.
+     * The duration of the operation is computed using the current
+     * timestamp and the given start time. If the duration meets
+     * or exceeds the configured value and is not throttled (determined by calling the
+     * generated method {@link #shouldThrottleCommit(long, long)}), an event will be
+     * emitted by calling {@link #commit(long, long, String, long, boolean)}
+     *
+     * @param start  the start time
+     * @param path  the path
+     * @param bytesRead  the number of bytes that were read, or -1 if the end of the file was reached
+     */
+    public static void offer(long start, String path, long bytesRead) {
+        long end = timestamp();
+        long duration = end - start;
+        if (shouldThrottleCommit(duration, end)) {
+            boolean endOfFile = bytesRead < 0;
+            long bytes = endOfFile ? 0 : bytesRead;
+            commit(start, duration, path, bytes, endOfFile);
+        }
+    }
+
     public static void commit(long start, long duration, String path, long bytesRead, boolean endOfFile) {
         // Generated by JFR
     }

src/java.base/share/classes/jdk/internal/event/FileWriteEvent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -44,11 +44,32 @@ public static long timestamp() {
         return 0L;
     }
 
-    public static boolean shouldCommit(long duration) {
+    public static boolean shouldThrottleCommit(long duration, long end) {
         // Generated by JFR
         return false;
     }
 
+    /**
+     * Helper method to offer the data needed to potentially commit an event.
+     * The duration of the operation is computed using the current
+     * timestamp and the given start time. If the duration meets
+     * or exceeds the configured value and is not throttled (determined by calling the
+     * generated method {@link #shouldThrottleCommit(long, long)}), an event will be
+     * emitted by calling {@link #commit(long, long, String, long)}
+     *
+     * @param start  the start time
+     * @param path  the path
+     * @param bytesRead  the number of bytes that were written, or -1 if the end of the file was reached
+     */
+    public static void offer(long start, String path, long bytesWritten) {
+        long end = timestamp();
+        long duration = end - start;
+        if (shouldThrottleCommit(duration, end)) {
+            long bytes = bytesWritten > 0 ? bytesWritten : 0;
+            commit(start, duration, path, bytes);
+        }
+    }
+
     public static void commit(long start, long duration, String path, long bytesWritten) {
         // Generated by JFR
     }

src/java.base/share/classes/jdk/internal/event/SocketReadEvent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2025, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -74,9 +74,10 @@ public static void commit(long start, long duration, String host, String address
      * of this method is generated automatically if jfr is enabled.
      *
      * @param duration  time in nanoseconds to complete the operation
+     * @param end  timestamp at the end of the operation
      * @return  true if the event should be commited
      */
-    public static boolean shouldCommit(long duration) {
+    public static boolean shouldThrottleCommit(long duration, long end) {
         // Generated by JFR
         return false;
     }
@@ -118,8 +119,9 @@ public static long timestamp() {
      * @param timeout  maximum time to wait
      */
     public static void offer(long start, long nbytes, SocketAddress remote, long timeout) {
-        long duration = timestamp() - start;
-        if (shouldCommit(duration)) {
+        long end = timestamp();
+        long duration = end - start;
+        if (shouldThrottleCommit(duration, end)) {
             emit(start, duration, nbytes, remote, timeout);
         }
     }