Trim reference tables when we trim the heap

Before:
System server:
 virtual                     shared   shared  private  private
  size      RSS      PSS    clean    dirty    clean    dirty    # object
2200      300      229        0       80        0      220   77 /dev/ashmem/dalvik-indirect ref table (deleted)
Location:
1896      128      102        0       28        0      100   39 /dev/ashmem/dalvik-indirect ref table (deleted)

After:
 virtual                     shared   shared  private  private
  size      RSS      PSS    clean    dirty    clean    dirty    # object
System server:
2216       64       64        0        0        0       64   79 /dev/ashmem/dalvik-indirect ref table (deleted)
Location:
2120       48       48        0        0        0       48   67 /dev/ashmem/dalvik-indirect ref table (deleted)

No pause time regression measured in memalloc test.

(cherry picked from commit 84dc99d2fa67e5dff018685661cb2bff62132989)

Change-Id: I80d9bd3b98e888fa8f77d03df69f8479ed209986

5 files changed, 48 insertions, 2 deletions

diff --git a/runtime/gc/heap.cc b/runtime/gc/heap.cc
index 0cceaa4467..7b679ea988 100644
--- a/runtime/gc/heap.cc
+++ b/runtime/gc/heap.cc
@@ -977,6 +977,22 @@ void Heap::DoPendingTransitionOrTrim() {
   Trim();
 }
 
+class TrimIndirectReferenceTableClosure : public Closure {
+ public:
+  explicit TrimIndirectReferenceTableClosure(Barrier* barrier) : barrier_(barrier) {
+  }
+  virtual void Run(Thread* thread) OVERRIDE NO_THREAD_SAFETY_ANALYSIS {
+    ATRACE_BEGIN("Trimming reference table");
+    thread->GetJniEnv()->locals.Trim();
+    ATRACE_END();
+    barrier_->Pass(Thread::Current());
+  }
+
+ private:
+  Barrier* const barrier_;
+};
+
+
 void Heap::Trim() {
   Thread* self = Thread::Current();
   {
@@ -998,6 +1014,19 @@ void Heap::Trim() {
     WaitForGcToCompleteLocked(kGcCauseTrim, self);
     collector_type_running_ = kCollectorTypeHeapTrim;
   }
+  // Trim reference tables.
+  {
+    ScopedObjectAccess soa(self);
+    JavaVMExt* vm = soa.Vm();
+    // Trim globals indirect reference table.
+    vm->TrimGlobals();
+    // Trim locals indirect reference tables.
+    Barrier barrier(0);
+    TrimIndirectReferenceTableClosure closure(&barrier);
+    ScopedThreadStateChange tsc(self, kWaitingForCheckPointsToRun);
+    size_t barrier_count = Runtime::Current()->GetThreadList()->RunCheckpoint(&closure);
+    barrier.Increment(self, barrier_count);
+  }
   uint64_t start_ns = NanoTime();
   // Trim the managed spaces.
   uint64_t total_alloc_space_allocated = 0;
diff --git a/runtime/indirect_reference_table.cc b/runtime/indirect_reference_table.cc
index 4d177a32d8..0d84a1ef98 100644
--- a/runtime/indirect_reference_table.cc
+++ b/runtime/indirect_reference_table.cc
@@ -162,13 +162,12 @@ bool IndirectReferenceTable::Remove(uint32_t cookie, IndirectRef iref) {
   DCHECK(table_ != NULL);
   DCHECK_GE(segment_state_.parts.numHoles, prevState.parts.numHoles);
 
-  int idx = ExtractIndex(iref);
-
   if (GetIndirectRefKind(iref) == kHandleScopeOrInvalid &&
       Thread::Current()->HandleScopeContains(reinterpret_cast<jobject>(iref))) {
     LOG(WARNING) << "Attempt to remove local handle scope entry from IRT, ignoring";
     return true;
   }
+  const int idx = ExtractIndex(iref);
   if (idx < bottomIndex) {
     // Wrong segment.
     LOG(WARNING) << "Attempt to remove index outside index area (" << idx
@@ -236,6 +235,13 @@ bool IndirectReferenceTable::Remove(uint32_t cookie, IndirectRef iref) {
   return true;
 }
 
+void IndirectReferenceTable::Trim() {
+  const size_t top_index = Capacity();
+  auto* release_start = AlignUp(reinterpret_cast<uint8_t*>(&table_[top_index]), kPageSize);
+  uint8_t* release_end = table_mem_map_->End();
+  madvise(release_start, release_end - release_start, MADV_DONTNEED);
+}
+
 void IndirectReferenceTable::VisitRoots(RootCallback* callback, void* arg, uint32_t tid,
                                         RootType root_type) {
   for (auto ref : *this) {
diff --git a/runtime/indirect_reference_table.h b/runtime/indirect_reference_table.h
index 168f9f2764..fbd5714688 100644
--- a/runtime/indirect_reference_table.h
+++ b/runtime/indirect_reference_table.h
@@ -331,6 +331,9 @@ class IndirectReferenceTable {
     return Offset(OFFSETOF_MEMBER(IndirectReferenceTable, segment_state_));
   }
 
+  // Release pages past the end of the table that may have previously held references.
+  void Trim() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+
  private:
   // Extract the table index from an indirect reference.
   static uint32_t ExtractIndex(IndirectRef iref) {
diff --git a/runtime/java_vm_ext.cc b/runtime/java_vm_ext.cc
index a5abce6ab1..5d04faccb5 100644
--- a/runtime/java_vm_ext.cc
+++ b/runtime/java_vm_ext.cc
@@ -756,6 +756,11 @@ void JavaVMExt::SweepJniWeakGlobals(IsMarkedCallback* callback, void* arg) {
   }
 }
 
+void JavaVMExt::TrimGlobals() {
+  WriterMutexLock mu(Thread::Current(), globals_lock_);
+  globals_.Trim();
+}
+
 void JavaVMExt::VisitRoots(RootCallback* callback, void* arg) {
   Thread* self = Thread::Current();
   {
diff --git a/runtime/java_vm_ext.h b/runtime/java_vm_ext.h
index 2957ba3fae..749b9fb6c0 100644
--- a/runtime/java_vm_ext.h
+++ b/runtime/java_vm_ext.h
@@ -131,6 +131,9 @@ class JavaVMExt : public JavaVM {
     return unchecked_functions_;
   }
 
+  void TrimGlobals() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
+      LOCKS_EXCLUDED(globals_lock_);
+
  private:
   Runtime* const runtime_;