RFR: 8269823: JFR: Eliminate 'is_large' check for native JFR event if the size range is certain [v4]

[Denghui Dong]

On Tue, 6 Jul 2021 06:19:07 GMT, Denghui Dong <ddong at openjdk.org> wrote:

>> Hi,
>> 
>> Could I have a review of this improvement that eliminates 'is_large' check if the event size range is certain?
>> 
>> JDK-8246260 introduced event large checks to reduce the recording size.
>> This check could be eliminated at compile/build time when one of the following conditions is satisfied:
>> 1. if the max size is < 128
>> 2. if the min size is >= 128
>> 
>> The max size and the min size could be computed for the most native events at the generation phase.
>> 
>> And I think this improvement may also be done for JDK events.
>
> Denghui Dong has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.

diff --git a/src/hotspot/share/jfr/jni/jfrJniMethod.cpp b/src/hotspot/share/jfr/jni/jfrJniMethod.cpp
index 54a4680ced8..893aaebdbd6 100644
--- a/src/hotspot/share/jfr/jni/jfrJniMethod.cpp
+++ b/src/hotspot/share/jfr/jni/jfrJniMethod.cpp
@@ -362,3 +362,11 @@ JVM_END
 JVM_ENTRY_NO_ENV(jboolean, jfr_set_handler(JNIEnv * env, jobject jvm, jobject clazz, jobject handler))
   return JfrJavaSupport::set_handler(clazz, handler, thread);
 JVM_END
+
+JVM_ENTRY_NO_ENV(void, jfr_emit(JNIEnv* env, jobject jvm))
+  for (int i = 0; i < 100; i++) {
+    EventTest e;
+    e.set_dummy(1);
+    e.commit();
+  }
+JVM_END
diff --git a/src/hotspot/share/jfr/jni/jfrJniMethod.hpp b/src/hotspot/share/jfr/jni/jfrJniMethod.hpp
index 19a676c4a22..7da213c80c1 100644
--- a/src/hotspot/share/jfr/jni/jfrJniMethod.hpp
+++ b/src/hotspot/share/jfr/jni/jfrJniMethod.hpp
@@ -152,6 +152,8 @@ jboolean JNICALL jfr_set_handler(JNIEnv* env, jobject jvm, jobject clazz, jobjec
 
 jlong JNICALL jfr_get_type_id_from_string(JNIEnv* env, jobject jvm, jstring type);
 
+void JNICALL jfr_emit(JNIEnv*, jobject jvm);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/src/hotspot/share/jfr/jni/jfrJniMethodRegistration.cpp b/src/hotspot/share/jfr/jni/jfrJniMethodRegistration.cpp
index db137776f65..1aab7909f6e 100644
--- a/src/hotspot/share/jfr/jni/jfrJniMethodRegistration.cpp
+++ b/src/hotspot/share/jfr/jni/jfrJniMethodRegistration.cpp
@@ -90,7 +90,8 @@ JfrJniMethodRegistration::JfrJniMethodRegistration(JNIEnv* env) {
       (char*)"getChunkStartNanos", (char*)"()J", (void*)jfr_chunk_start_nanos,
       (char*)"getHandler", (char*)"(Ljava/lang/Class;)Ljava/lang/Object;", (void*)jfr_get_handler,
       (char*)"setHandler", (char*)"(Ljava/lang/Class;Ljdk/jfr/internal/handlers/EventHandler;)Z", (void*)jfr_set_handler,
-      (char*)"getTypeId", (char*)"(Ljava/lang/String;)J", (void*)jfr_get_type_id_from_string
+      (char*)"getTypeId", (char*)"(Ljava/lang/String;)J", (void*)jfr_get_type_id_from_string,
+      (char*)"emit", (char*)"()V", (void*)jfr_emit,
     };
 
     const size_t method_array_length = sizeof(method) / sizeof(JNINativeMethod);
diff --git a/src/hotspot/share/jfr/metadata/metadata.xml b/src/hotspot/share/jfr/metadata/metadata.xml
index 1a19b763314..633c6e3f1f1 100644
--- a/src/hotspot/share/jfr/metadata/metadata.xml
+++ b/src/hotspot/share/jfr/metadata/metadata.xml
@@ -1081,6 +1081,10 @@
     <Field type="uint" name="stallCount" label="Stall Count" description="The number of Java threads stalled by the GC locker" />
   </Event>
 
+  <Event name="Test" category="Test" label="Dummy">
+    <Field type="uint" name="dummy" label="Dummy" description="Dummy" />
+  </Event>
+
   <Type name="DeoptimizationReason" label="Deoptimization Reason">
     <Field type="string" name="reason" label="Reason" />
   </Type>
diff --git a/src/jdk.jfr/share/classes/jdk/jfr/internal/JVM.java b/src/jdk.jfr/share/classes/jdk/jfr/internal/JVM.java
index a88b428dac3..bd28e5b4015 100644
--- a/src/jdk.jfr/share/classes/jdk/jfr/internal/JVM.java
+++ b/src/jdk.jfr/share/classes/jdk/jfr/internal/JVM.java
@@ -597,4 +597,6 @@ public final class JVM {
      * @return the id, or a negative value if it does not exists.
      */
     public native long getTypeId(String name);
+
+    public native void emit();
 }


It's a simple benchmark, I wrote a native function to emit 100 same native events.

package org.sample;

import jdk.jfr.Event;
import jdk.jfr.Recording;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Warmup;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.*;
import org.openjdk.jmh.infra.Blackhole;
import jdk.jfr.internal.JVM;

@State(Scope.Benchmark)
public class MyBenchmark {


    @Benchmark
    @Fork(value=1, jvmArgs = {"--add-exports", "jdk.jfr/jdk.jfr.internal=ALL-UNNAMED"})
    @Warmup(iterations = 5, time = 1)
    public void testEmit(Blackhole bh) {
        JVM.getJVM().emit();
    }
}

-------------

PR: https://git.openjdk.java.net/jdk/pull/4670