Improve accounting of native roots in hprof
Native roots from VisitReferences are not real roots, they are
actually references held live by the object. Instead of
reporting these as roots in hprof, report them as objects in a
runtimeInternalObjects field containing an object array.
Also added runtimeInternalObjects to dex caches.
Changed non-app image and zygote space objects to be roots since
this is how the GC treats them.
These changes make it easier to debug class unloading since you
can more easily see the path to root keeping a dex cache or
classloader live.
Bug: 36457259
Bug: 22720414
Test: test/run-test --host 130
Test: take hprof dump and look at a class loader
Change-Id: I089b2aed6831043160f0657a46cf71087d1cdbb6
diff --git a/runtime/hprof/hprof.cc b/runtime/hprof/hprof.cc
index 4f390fd..8bdf6b1 100644
--- a/runtime/hprof/hprof.cc
+++ b/runtime/hprof/hprof.cc
@@ -34,7 +34,6 @@
#include <time.h>
#include <time.h>
#include <unistd.h>
-
#include <set>
#include "android-base/stringprintf.h"
@@ -502,9 +501,16 @@
void DumpHeapArray(mirror::Array* obj, mirror::Class* klass)
REQUIRES_SHARED(Locks::mutator_lock_);
- void DumpHeapInstanceObject(mirror::Object* obj, mirror::Class* klass)
+ void DumpFakeObjectArray(mirror::Object* obj, const std::set<mirror::Object*>& elements)
REQUIRES_SHARED(Locks::mutator_lock_);
+ void DumpHeapInstanceObject(mirror::Object* obj,
+ mirror::Class* klass,
+ const std::set<mirror::Object*>& fake_roots)
+ REQUIRES_SHARED(Locks::mutator_lock_);
+
+ bool AddRuntimeInternalObjectsField(mirror::Class* klass) REQUIRES_SHARED(Locks::mutator_lock_);
+
void ProcessHeap(bool header_first)
REQUIRES(Locks::mutator_lock_) {
// Reset current heap and object count.
@@ -1062,37 +1068,17 @@
++objects_in_segment_;
}
-// Use for visiting the GcRoots held live by ArtFields, ArtMethods, and ClassLoaders.
-class GcRootVisitor {
- public:
- explicit GcRootVisitor(Hprof* hprof) : hprof_(hprof) {}
-
- void operator()(mirror::Object* obj ATTRIBUTE_UNUSED,
- MemberOffset offset ATTRIBUTE_UNUSED,
- bool is_static ATTRIBUTE_UNUSED) const {}
-
- // Note that these don't have read barriers. Its OK however since the GC is guaranteed to not be
- // running during the hprof dumping process.
- void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const
- REQUIRES_SHARED(Locks::mutator_lock_) {
- if (!root->IsNull()) {
- VisitRoot(root);
- }
+bool Hprof::AddRuntimeInternalObjectsField(mirror::Class* klass) {
+ if (klass->IsDexCacheClass()) {
+ return true;
}
-
- void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const
- REQUIRES_SHARED(Locks::mutator_lock_) {
- mirror::Object* obj = root->AsMirrorPtr();
- // The two cases are either classes or dex cache arrays. If it is a dex cache array, then use
- // VM internal. Otherwise the object is a declaring class of an ArtField or ArtMethod or a
- // class from a ClassLoader.
- hprof_->VisitRoot(obj, RootInfo(obj->IsClass() ? kRootStickyClass : kRootVMInternal));
+ // IsClassLoaderClass is true for subclasses of classloader but we only want to add the fake
+ // field to the java.lang.ClassLoader class.
+ if (klass->IsClassLoaderClass() && klass->GetSuperClass()->IsObjectClass()) {
+ return true;
}
-
-
- private:
- Hprof* const hprof_;
-};
+ return false;
+}
void Hprof::DumpHeapObject(mirror::Object* obj) {
// Ignore classes that are retired.
@@ -1103,8 +1089,41 @@
++total_objects_;
- GcRootVisitor visitor(this);
- obj->VisitReferences(visitor, VoidFunctor());
+ class RootCollector {
+ public:
+ explicit RootCollector() {}
+
+ void operator()(mirror::Object*, MemberOffset, bool) const {}
+
+ // Note that these don't have read barriers. Its OK however since the GC is guaranteed to not be
+ // running during the hprof dumping process.
+ void VisitRootIfNonNull(mirror::CompressedReference<mirror::Object>* root) const
+ REQUIRES_SHARED(Locks::mutator_lock_) {
+ if (!root->IsNull()) {
+ VisitRoot(root);
+ }
+ }
+
+ void VisitRoot(mirror::CompressedReference<mirror::Object>* root) const
+ REQUIRES_SHARED(Locks::mutator_lock_) {
+ roots_.insert(root->AsMirrorPtr());
+ }
+
+ const std::set<mirror::Object*>& GetRoots() const {
+ return roots_;
+ }
+
+ private:
+ // These roots are actually live from the object. Avoid marking them as roots in hprof to make
+ // it easier to debug class unloading.
+ mutable std::set<mirror::Object*> roots_;
+ };
+
+ RootCollector visitor;
+ // Collect all native roots.
+ if (!obj->IsClass()) {
+ obj->VisitReferences(visitor, VoidFunctor());
+ }
gc::Heap* const heap = Runtime::Current()->GetHeap();
const gc::space::ContinuousSpace* const space = heap->FindContinuousSpaceFromObject(obj, true);
@@ -1112,15 +1131,18 @@
if (space != nullptr) {
if (space->IsZygoteSpace()) {
heap_type = HPROF_HEAP_ZYGOTE;
+ VisitRoot(obj, RootInfo(kRootVMInternal));
} else if (space->IsImageSpace() && heap->ObjectIsInBootImageSpace(obj)) {
// Only count objects in the boot image as HPROF_HEAP_IMAGE, this leaves app image objects as
// HPROF_HEAP_APP. b/35762934
heap_type = HPROF_HEAP_IMAGE;
+ VisitRoot(obj, RootInfo(kRootVMInternal));
}
} else {
const auto* los = heap->GetLargeObjectsSpace();
if (los->Contains(obj) && los->IsZygoteLargeObject(Thread::Current(), obj)) {
heap_type = HPROF_HEAP_ZYGOTE;
+ VisitRoot(obj, RootInfo(kRootVMInternal));
}
}
CheckHeapSegmentConstraints();
@@ -1164,7 +1186,7 @@
} else if (c->IsArrayClass()) {
DumpHeapArray(obj->AsArray(), c);
} else {
- DumpHeapInstanceObject(obj, c);
+ DumpHeapInstanceObject(obj, c, visitor.GetRoots());
}
}
@@ -1269,7 +1291,10 @@
// Instance fields for this class (no superclass fields)
int iFieldCount = klass->NumInstanceFields();
- if (klass->IsStringClass()) {
+ // add_internal_runtime_objects is only for classes that may retain objects live through means
+ // other than fields. It is never the case for strings.
+ const bool add_internal_runtime_objects = AddRuntimeInternalObjectsField(klass);
+ if (klass->IsStringClass() || add_internal_runtime_objects) {
__ AddU2((uint16_t)iFieldCount + 1);
} else {
__ AddU2((uint16_t)iFieldCount);
@@ -1284,6 +1309,21 @@
if (klass->IsStringClass()) {
__ AddStringId(LookupStringId("value"));
__ AddU1(hprof_basic_object);
+ } else if (add_internal_runtime_objects) {
+ __ AddStringId(LookupStringId("runtimeInternalObjects"));
+ __ AddU1(hprof_basic_object);
+ }
+}
+
+void Hprof::DumpFakeObjectArray(mirror::Object* obj, const std::set<mirror::Object*>& elements) {
+ __ AddU1(HPROF_OBJECT_ARRAY_DUMP);
+ __ AddObjectId(obj);
+ __ AddStackTraceSerialNumber(LookupStackTraceSerialNumber(obj));
+ __ AddU4(elements.size());
+ __ AddClassId(LookupClassId(
+ Runtime::Current()->GetClassLinker()->GetClassRoot(ClassLinker::kObjectArrayClass)));
+ for (mirror::Object* e : elements) {
+ __ AddObjectId(e);
}
}
@@ -1327,7 +1367,9 @@
}
}
-void Hprof::DumpHeapInstanceObject(mirror::Object* obj, mirror::Class* klass) {
+void Hprof::DumpHeapInstanceObject(mirror::Object* obj,
+ mirror::Class* klass,
+ const std::set<mirror::Object*>& fake_roots) {
// obj is an instance object.
__ AddU1(HPROF_INSTANCE_DUMP);
__ AddObjectId(obj);
@@ -1341,6 +1383,7 @@
// What we will use for the string value if the object is a string.
mirror::Object* string_value = nullptr;
+ mirror::Object* fake_object_array = nullptr;
// Write the instance data; fields for this class, followed by super class fields, and so on.
do {
@@ -1396,8 +1439,12 @@
}
}
__ AddObjectId(string_value);
+ } else if (AddRuntimeInternalObjectsField(klass)) {
+ // We need an id that is guaranteed to not be used, use 1/2 of the object alignment.
+ fake_object_array = reinterpret_cast<mirror::Object*>(
+ reinterpret_cast<uintptr_t>(obj) + kObjectAlignment / 2);
+ __ AddObjectId(fake_object_array);
}
-
klass = klass->GetSuperClass();
} while (klass != nullptr);
@@ -1419,6 +1466,8 @@
__ AddU1(hprof_basic_char);
__ AddU2List(s->GetValue(), s->GetLength());
}
+ } else if (fake_object_array != nullptr) {
+ DumpFakeObjectArray(fake_object_array, fake_roots);
}
}