RFR: 8351640: Print reason for making method not entrant [v2]

[Vladimir Ivanov]

On Wed, 12 Mar 2025 07:35:33 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> A simple quality of life improvement. We are studying compiler dynamics in Leyden, and it would be convenient to know why the particular methods are marked as not entrant. We just need to pass the extra string argument to `nmethod::make_not_entrant` and print it out. 
>> 
>> Sample log excerpt for mainline:
>> 
>> 
>> $ grep com.sun.tools.javac.util.IntHashTable::lookup print-compilation.log 
>> 987   780       3       com.sun.tools.javac.util.IntHashTable::lookup (100 bytes)
>> 1019  877       4       com.sun.tools.javac.util.IntHashTable::lookup (100 bytes)
>> 1024  780       3       com.sun.tools.javac.util.IntHashTable::lookup (100 bytes)   made not entrant: not used
>> 4995  877       4       com.sun.tools.javac.util.IntHashTable::lookup (100 bytes)   made not entrant: uncommon trap
>> 5287 3734       3       com.sun.tools.javac.util.IntHashTable::lookup (100 bytes)
>> 6615 5472       4       com.sun.tools.javac.util.IntHashTable::lookup (100 bytes)
>> 6626 3734       3       com.sun.tools.javac.util.IntHashTable::lookup (100 bytes)   made not entrant: not used
>> 
>> 
>> You can now clearly see the method lifecycle. 1 second in app lifetime, the method was initially compiled at level 3. Shortly after, it got compiled at level 4, turning level 3 method unused. 4 seconds later, level 4 method encountered uncommon trap, so we are back to level 3. After 1.3 seconds more, the final compilation at level 4 completed, and second level 3 compilation was removed as unused.
>> 
>> Additional testing:
>>  - [x] Linux x86_64 server fastdebug, `hotspot:tier1`
>>  - [x] Linux x86_64 server fastdebug, `all`
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Add to LogCompilation as well
>  - Merge branch 'master' into JDK-8351640-nmethod-not-entrant-reason
>  - Use resource allocation for temp buffer
>  - Base version

Looks good. 

Do you mind incorporating log compilation tool support? [1]


diff --git a/src/utils/LogCompilation/src/main/java/com/sun/hotspot/tools/compiler/LogParser.java b/src/utils/LogCompilation/src/main/java/com/sun/hotspot/tools/compiler/LogParser.java
index e1e305abe10..61cbc054200 100644
--- a/src/utils/LogCompilation/src/main/java/com/sun/hotspot/tools/compiler/LogParser.java
+++ b/src/utils/LogCompilation/src/main/java/com/sun/hotspot/tools/compiler/LogParser.java
@@ -1099,6 +1099,10 @@ public void startElement(String uri, String localName, String qname, Attributes
             e.setCompileKind(compileKind);
             String level = atts.getValue("level");
             e.setLevel(level);
+            String reason = atts.getValue("reason");
+            if (reason != null) {
+              e.setReason(reason);
+            }
             events.add(e);
         } else if (qname.equals("uncommon_trap")) {
             String id = atts.getValue("compile_id");
diff --git a/src/utils/LogCompilation/src/main/java/com/sun/hotspot/tools/compiler/MakeNotEntrantEvent.java b/src/utils/LogCompilation/src/main/java/com/sun/hotspot/tools/compiler/MakeNotEntrantEvent.java
index b4015537c74..d230f1b4336 100644
--- a/src/utils/LogCompilation/src/main/java/com/sun/hotspot/tools/compiler/MakeNotEntrantEvent.java
+++ b/src/utils/LogCompilation/src/main/java/com/sun/hotspot/tools/compiler/MakeNotEntrantEvent.java
@@ -47,6 +47,11 @@ class MakeNotEntrantEvent extends BasicLogEvent {
      */
     private String level;
 
+    /**
+     * The reason of invalidation.
+     */
+    private String reason;
+
     /**
      * The compile kind.
      */
@@ -64,10 +69,14 @@ public NMethod getNMethod() {
 
     public void print(PrintStream stream, boolean printID) {
         if (isZombie()) {
-            stream.printf("%s make_zombie\n", getId());
+            stream.printf("%s make_zombie", getId());
         } else {
-            stream.printf("%s make_not_entrant\n", getId());
+            stream.printf("%s make_not_entrant", getId());
+        }
+        if (getReason() != null) {
+            stream.printf(": %s", getReason());
         }
+        stream.println();
     }
 
     public boolean isZombie() {
@@ -88,7 +97,21 @@ public void setLevel(String level) {
       this.level = level;
   }
 
-    /**
+  /**
+   * @return the reason
+   */
+  public String getReason() {
+      return reason;
+  }
+
+  /**
+   * @param reason the reason to set
+   */
+  public void setReason(String reason) {
+      this.reason = reason;
+  }
+
+  /**
    * @return the compileKind
    */
   public String getCompileKind() {

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PR Review: https://git.openjdk.org/jdk/pull/23980#pullrequestreview-2679301582