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8365400: enhance JFR to emit file and module metadata for class loading #27738

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8365400: enhance JFR to emit file and module metadata for class loading #27738

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524d23e
JDK-8365400: added jdk.ClassFileDefine JFR event to record class file…
lpgc Oct 8, 2025
09ce247
JDK-8365400: changed field label, and normalized value of 'source' wh…
lpgc Oct 9, 2025
67141ee
added package and module entries
lpgc Oct 16, 2025
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8 changes: 8 additions & 0 deletions src/hotspot/share/jfr/metadata/metadata.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -217,6 +217,14 @@
<Field type="ClassLoader" name="definingClassLoader" label="Defining Class Loader" />
</Event>

<Event name="ClassFileDefine" category="Java Virtual Machine, Class Loading" label="ClassFile Definition" thread="true" stackTrace="true" startTime="false">
<Field type="Class" name="definedClass" label="Defined Class" />
<Field type="string" name="source" label="ClassFile Location" />
<Field type="string" name="package" label="Package Name" />
<Field type="string" name="module" label="Module Name" />
<Field type="ClassLoader" name="definingClassLoader" label="Defining Class Loader" />
</Event>

<Event name="ClassRedefinition" category="Java Virtual Machine, Class Loading" label="Class Redefinition" thread="false" stackTrace="false" startTime="false">
<Field type="Class" name="redefinedClass" label="Redefined Class" />
<Field type="int" name="classModificationCount" label="Class Modification Count" description="The number of times the class has changed"/>
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22 changes: 19 additions & 3 deletions src/hotspot/share/prims/jvm.cpp
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Expand Up @@ -860,8 +860,6 @@ static jclass jvm_define_class_common(const char *name,
jobject loader, const jbyte *buf,
jsize len, jobject pd, const char *source,
TRAPS) {
if (source == nullptr) source = "__JVM_DefineClass__";

JavaThread* jt = THREAD;

PerfClassTraceTime vmtimer(ClassLoader::perf_define_appclass_time(),
Expand All @@ -881,10 +879,13 @@ static jclass jvm_define_class_common(const char *name,
CHECK_NULL);

ResourceMark rm(THREAD);
ClassFileStream st((u1*)buf, len, source);
ClassFileStream st((u1*)buf, len, source != nullptr ? source : "__JVM_DefineClass__");
Handle class_loader (THREAD, JNIHandles::resolve(loader));
Handle protection_domain (THREAD, JNIHandles::resolve(pd));
ClassLoadInfo cl_info(protection_domain);

EventClassFileDefine cfd_evt;

Klass* k = SystemDictionary::resolve_from_stream(&st, class_name,
class_loader,
cl_info,
Expand All @@ -894,6 +895,21 @@ static jclass jvm_define_class_common(const char *name,
trace_class_resolution(k);
}

if (cfd_evt.should_commit()) {
cfd_evt.set_definedClass(k);
cfd_evt.set_source(source != nullptr ? source : "jrt://");
cfd_evt.set_definingClassLoader(k->class_loader_data());

const PackageEntry *const package = k->package();

cfd_evt.set_package(package->name()->as_C_string());
const ModuleEntry *const module = k->module();

cfd_evt.set_module(module->is_named() ? module->name()->as_C_string() : UNNAMED_MODULE);

cfd_evt.commit();
}

return (jclass) JNIHandles::make_local(THREAD, k->java_mirror());
}

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5 changes: 5 additions & 0 deletions src/jdk.jfr/share/conf/jfr/default.jfc
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Expand Up @@ -166,6 +166,11 @@
<setting name="stackTrace">true</setting>
</event>

<event name="jdk.ClassFileDefine">
<setting name="enabled" control="class-loading">false</setting>
<setting name="stackTrace">true</setting>
</event>

<event name="jdk.RedefineClasses">
<setting name="enabled">true</setting>
<setting name="stackTrace">true</setting>
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5 changes: 5 additions & 0 deletions src/jdk.jfr/share/conf/jfr/profile.jfc
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Expand Up @@ -166,6 +166,11 @@
<setting name="stackTrace">true</setting>
</event>

<event name="jdk.ClassFileDefine">
<setting name="enabled" control="class-loading">false</setting>
<setting name="stackTrace">true</setting>
</event>

<event name="jdk.RedefineClasses">
<setting name="enabled">true</setting>
<setting name="stackTrace">true</setting>
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