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

Change-Id: Ib3116953df7adafdc1560b064365c8b56e71483e

1 files changed, 10 insertions, 1 deletions

diff --git a/compiler/image_writer.cc b/compiler/image_writer.cc
index c747ffa65b..8bb462c667 100644
--- a/compiler/image_writer.cc
+++ b/compiler/image_writer.cc
@@ -576,7 +576,16 @@ void ImageWriter::AssignImageBinSlot(mirror::Object* object) {
       }
     } 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);