Always use an array in the DexCache for ArtField and ArtMethod.

The lookup success rate is too low (<1%) during app startup where the
cache is most stressed. So always use an array for them.

To avoid memory regression, madvise away the arrays at every GC.

go/art-benchmark-service reports ~3% improvement in app startup with no
statistically significant memory regression.

Test: test.py
Change-Id: Id13612054943ed7770c9e96756f391eed2352d79

1 files changed, 16 insertions, 0 deletions

diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index 090ee42a08..5d76f802ee 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -10977,8 +10977,24 @@ void ClassLinker::InsertDexFileInToClassLoader(ObjPtr<mirror::Object> dex_file,
   }
 }
 
+class ReclaimMemoryDexCacheVisitor : public DexCacheVisitor {
+ public:
+  ReclaimMemoryDexCacheVisitor() {}
+
+  void Visit(ObjPtr<mirror::DexCache> dex_cache)
+      REQUIRES_SHARED(Locks::dex_lock_, Locks::mutator_lock_) override {
+    dex_cache->ReclaimMemory();
+  }
+};
+
 void ClassLinker::CleanupClassLoaders() {
   Thread* const self = Thread::Current();
+  // We clear dex cache arrays for every GC.
+  {
+    ReaderMutexLock mu(self, *Locks::dex_lock_);
+    ReclaimMemoryDexCacheVisitor visitor;
+    VisitDexCaches(&visitor);
+  }
   std::list<ClassLoaderData> to_delete;
   // Do the delete outside the lock to avoid lock violation in jit code cache.
   {