Reduce dirty image pages by improving binning

Change ordering from dirty to less dirty since ArtFields are clean
and they are last. Add separate binning for DexCache and instances
of java lang object (probably a lock object).

Business card .art RAM (on shamu):
              PSS     Private Dirty
.art mmap     1011      600
.art mmap      990      560

Bug: 27906566

(cherry picked from commit 794bff5f622c79fd7bd9899e700cf052a375c675)

Change-Id: I31c9ff41c3d713fc3b14573c2b731325ac6f366f
diff --git a/compiler/image_writer.cc b/compiler/image_writer.cc
index c747ffa..8bb462c 100644
--- a/compiler/image_writer.cc
+++ b/compiler/image_writer.cc
@@ -576,7 +576,16 @@
       }
     } else if (object->GetClass<kVerifyNone>()->IsStringClass()) {
       bin = kBinString;  // Strings are almost always immutable (except for object header).
-    }  // else bin = kBinRegular
+    } else if (object->GetClass<kVerifyNone>() ==
+        Runtime::Current()->GetClassLinker()->GetClassRoot(ClassLinker::kJavaLangObject)) {
+      // Instance of java lang object, probably a lock object. This means it will be dirty when we
+      // synchronize on it.
+      bin = kBinMiscDirty;
+    } else if (object->IsDexCache()) {
+      // Dex file field becomes dirty when the image is loaded.
+      bin = kBinMiscDirty;
+    }
+    // else bin = kBinRegular
   }
 
   size_t oat_index = GetOatIndex(object);
diff --git a/compiler/image_writer.h b/compiler/image_writer.h
index f204b28..0cb6aea 100644
--- a/compiler/image_writer.h
+++ b/compiler/image_writer.h
@@ -149,16 +149,17 @@
   void RecordImageAllocations() SHARED_REQUIRES(Locks::mutator_lock_);
 
   // Classify different kinds of bins that objects end up getting packed into during image writing.
+  // Ordered from dirtiest to cleanest (until ArtMethods).
   enum Bin {
-    // Likely-clean:
-    kBinString,                        // [String] Almost always immutable (except for obj header).
+    kBinMiscDirty,                // Dex caches, object locks, etc...
+    kBinClassVerified,            // Class verified, but initializers haven't been run
     // Unknown mix of clean/dirty:
     kBinRegular,
-    // Likely-dirty:
+    kBinClassInitialized,         // Class initializers have been run
     // All classes get their own bins since their fields often dirty
     kBinClassInitializedFinalStatics,  // Class initializers have been run, no non-final statics
-    kBinClassInitialized,         // Class initializers have been run
-    kBinClassVerified,            // Class verified, but initializers haven't been run
+    // Likely-clean:
+    kBinString,                        // [String] Almost always immutable (except for obj header).
     // Add more bins here if we add more segregation code.
     // Non mirror fields must be below.
     // ArtFields should be always clean.
diff --git a/imgdiag/imgdiag.cc b/imgdiag/imgdiag.cc
index c2a812e..cbd0c40 100644
--- a/imgdiag/imgdiag.cc
+++ b/imgdiag/imgdiag.cc
@@ -416,7 +416,8 @@
     // Look up local classes by their descriptor
     std::map<std::string, mirror::Class*> local_class_map;
 
-    std::unordered_set<mirror::Object*> dirty_objects;
+    // Use set to have sorted output.
+    std::set<mirror::Object*> dirty_objects;
 
     size_t dirty_object_bytes = 0;
     const uint8_t* begin_image_ptr = image_begin_unaligned;