diff --git a/java/src/com/android/inputmethod/latin/BinaryDictionary.java b/java/src/com/android/inputmethod/latin/BinaryDictionary.java
index dae56b5..709b0a1 100644
--- a/java/src/com/android/inputmethod/latin/BinaryDictionary.java
+++ b/java/src/com/android/inputmethod/latin/BinaryDictionary.java
@@ -19,6 +19,7 @@
 import android.text.TextUtils;
 import android.util.SparseArray;
 
+import com.android.inputmethod.annotations.UsedForTesting;
 import com.android.inputmethod.keyboard.ProximityInfo;
 import com.android.inputmethod.latin.SuggestedWords.SuggestedWordInfo;
 import com.android.inputmethod.latin.settings.NativeSuggestOptions;
@@ -47,6 +48,7 @@
     private long mNativeDict;
     private final Locale mLocale;
     private final long mDictSize;
+    private final String mDictFilePath;
     private final int[] mInputCodePoints = new int[MAX_WORD_LENGTH];
     private final int[] mOutputCodePoints = new int[MAX_WORD_LENGTH * MAX_RESULTS];
     private final int[] mSpaceIndices = new int[MAX_RESULTS];
@@ -91,6 +93,7 @@
         super(dictType);
         mLocale = locale;
         mDictSize = length;
+        mDictFilePath = filename;
         mNativeSuggestOptions.setUseFullEditDistance(useFullEditDistance);
         loadDictionary(filename, offset, length, isUpdatable);
     }
@@ -101,6 +104,9 @@
 
     private static native long openNative(String sourceDir, long dictOffset, long dictSize,
             boolean isUpdatable);
+    private static native void flushNative(long dict, String filePath);
+    private static native boolean needsToRunGCNative(long dict);
+    private static native void flushWithGCNative(long dict, String filePath);
     private static native void closeNative(long dict);
     private static native int getProbabilityNative(long dict, int[] word);
     private static native boolean isValidBigramNative(long dict, int[] word0, int[] word1);
@@ -261,6 +267,24 @@
         removeBigramWordsNative(mNativeDict, codePoints0, codePoints1);
     }
 
+    @UsedForTesting
+    public void flush() {
+        if (!isValidDictionary()) return;
+        flushNative(mNativeDict, mDictFilePath);
+    }
+
+    @UsedForTesting
+    public void flushWithGC() {
+        if (!isValidDictionary()) return;
+        flushWithGCNative(mNativeDict, mDictFilePath);
+    }
+
+    @UsedForTesting
+    public boolean needsToRunGC() {
+        if (!isValidDictionary()) return false;
+        return needsToRunGCNative(mNativeDict);
+    }
+
     @Override
     public boolean shouldAutoCommit(final SuggestedWordInfo candidate) {
         // TODO: actually use the confidence rather than use this completely broken heuristic
diff --git a/native/jni/com_android_inputmethod_latin_BinaryDictionary.cpp b/native/jni/com_android_inputmethod_latin_BinaryDictionary.cpp
index 6a36612..a63fab6 100644
--- a/native/jni/com_android_inputmethod_latin_BinaryDictionary.cpp
+++ b/native/jni/com_android_inputmethod_latin_BinaryDictionary.cpp
@@ -46,8 +46,7 @@
     sourceDirChars[sourceDirUtf8Length] = '\0';
     DictionaryStructureWithBufferPolicy *const dictionaryStructureWithBufferPolicy =
             DictionaryStructureWithBufferPolicyFactory::newDictionaryStructureWithBufferPolicy(
-                    sourceDirChars, static_cast<int>(sourceDirUtf8Length),
-                    static_cast<int>(dictOffset), static_cast<int>(dictSize),
+                    sourceDirChars, static_cast<int>(dictOffset), static_cast<int>(dictSize),
                     isUpdatable == JNI_TRUE);
     if (!dictionaryStructureWithBufferPolicy) {
         return 0;
@@ -59,6 +58,35 @@
     return reinterpret_cast<jlong>(dictionary);
 }
 
+static void latinime_BinaryDictionary_flush(JNIEnv *env, jclass clazz, jlong dict,
+        jstring filePath) {
+    Dictionary *dictionary = reinterpret_cast<Dictionary *>(dict);
+    if (!dictionary) return;
+    const jsize filePathUtf8Length = env->GetStringUTFLength(filePath);
+    char filePathChars[filePathUtf8Length + 1];
+    env->GetStringUTFRegion(filePath, 0, env->GetStringLength(filePath), filePathChars);
+    filePathChars[filePathUtf8Length] = '\0';
+    dictionary->flush(filePathChars);
+}
+
+static bool latinime_BinaryDictionary_needsToRunGC(JNIEnv *env, jclass clazz,
+        jlong dict) {
+    Dictionary *dictionary = reinterpret_cast<Dictionary *>(dict);
+    if (!dictionary) return false;
+    return dictionary->needsToRunGC();
+}
+
+static void latinime_BinaryDictionary_flushWithGC(JNIEnv *env, jclass clazz, jlong dict,
+        jstring filePath) {
+    Dictionary *dictionary = reinterpret_cast<Dictionary *>(dict);
+    if (!dictionary) return;
+    const jsize filePathUtf8Length = env->GetStringUTFLength(filePath);
+    char filePathChars[filePathUtf8Length + 1];
+    env->GetStringUTFRegion(filePath, 0, env->GetStringLength(filePath), filePathChars);
+    filePathChars[filePathUtf8Length] = '\0';
+    dictionary->flushWithGC(filePathChars);
+}
+
 static void latinime_BinaryDictionary_close(JNIEnv *env, jclass clazz, jlong dict) {
     Dictionary *dictionary = reinterpret_cast<Dictionary *>(dict);
     if (!dictionary) return;
@@ -253,6 +281,21 @@
         reinterpret_cast<void *>(latinime_BinaryDictionary_close)
     },
     {
+        const_cast<char *>("flushNative"),
+        const_cast<char *>("(JLjava/lang/String;)V"),
+        reinterpret_cast<void *>(latinime_BinaryDictionary_flush)
+    },
+    {
+        const_cast<char *>("needsToRunGCNative"),
+        const_cast<char *>("(J)Z"),
+        reinterpret_cast<void *>(latinime_BinaryDictionary_needsToRunGC)
+    },
+    {
+        const_cast<char *>("flushWithGCNative"),
+        const_cast<char *>("(JLjava/lang/String;)V"),
+        reinterpret_cast<void *>(latinime_BinaryDictionary_flushWithGC)
+    },
+    {
         const_cast<char *>("getSuggestionsNative"),
         const_cast<char *>("(JJJ[I[I[I[I[III[I[I[I[I[I[I[I)I"),
         reinterpret_cast<void *>(latinime_BinaryDictionary_getSuggestions)
diff --git a/native/jni/src/suggest/core/dictionary/dictionary.cpp b/native/jni/src/suggest/core/dictionary/dictionary.cpp
index 29fe7ab..0335722 100644
--- a/native/jni/src/suggest/core/dictionary/dictionary.cpp
+++ b/native/jni/src/suggest/core/dictionary/dictionary.cpp
@@ -112,6 +112,18 @@
     mDictionaryStructureWithBufferPolicy->removeBigramWords(word0, length0, word1, length1);
 }
 
+void Dictionary::flush(const char *const filePath) {
+    mDictionaryStructureWithBufferPolicy->flush(filePath);
+}
+
+void Dictionary::flushWithGC(const char *const filePath) {
+    mDictionaryStructureWithBufferPolicy->flushWithGC(filePath);
+}
+
+bool Dictionary::needsToRunGC() {
+    return mDictionaryStructureWithBufferPolicy->needsToRunGC();
+}
+
 void Dictionary::logDictionaryInfo(JNIEnv *const env) const {
     const int BUFFER_SIZE = 16;
     int dictionaryIdCodePointBuffer[BUFFER_SIZE];
diff --git a/native/jni/src/suggest/core/dictionary/dictionary.h b/native/jni/src/suggest/core/dictionary/dictionary.h
index 0afe5a5..06e84bb 100644
--- a/native/jni/src/suggest/core/dictionary/dictionary.h
+++ b/native/jni/src/suggest/core/dictionary/dictionary.h
@@ -77,6 +77,12 @@
     void removeBigramWords(const int *const word0, const int length0, const int *const word1,
             const int length1);
 
+    void flush(const char *const filePath);
+
+    void flushWithGC(const char *const filePath);
+
+    bool needsToRunGC();
+
     const DictionaryStructureWithBufferPolicy *getDictionaryStructurePolicy() const {
         return mDictionaryStructureWithBufferPolicy;
     }
diff --git a/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h b/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h
index c8cbbcf..24d1b8b 100644
--- a/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h
+++ b/native/jni/src/suggest/core/policy/dictionary_structure_with_buffer_policy.h
@@ -74,6 +74,12 @@
     virtual bool removeBigramWords(const int *const word0, const int length0,
             const int *const word1, const int length1) = 0;
 
+    virtual void flush(const char *const filePath) = 0;
+
+    virtual void flushWithGC(const char *const filePath) = 0;
+
+    virtual bool needsToRunGC() const = 0;
+
  protected:
     DictionaryStructureWithBufferPolicy() {}
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.cpp b/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.cpp
index 434858d..ff80dd2 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.cpp
@@ -27,12 +27,12 @@
 namespace latinime {
 
 /* static */ DictionaryStructureWithBufferPolicy *DictionaryStructureWithBufferPolicyFactory
-        ::newDictionaryStructureWithBufferPolicy(const char *const path, const int pathLength,
-                const int bufOffset, const int size, const bool isUpdatable) {
+        ::newDictionaryStructureWithBufferPolicy(const char *const path, const int bufOffset,
+                const int size, const bool isUpdatable) {
     // Allocated buffer in MmapedBuffer::openBuffer() will be freed in the destructor of
     // impl classes of DictionaryStructureWithBufferPolicy.
-    const MmappedBuffer *const mmapedBuffer = MmappedBuffer::openBuffer(path, pathLength, bufOffset,
-            size, isUpdatable);
+    const MmappedBuffer *const mmapedBuffer = MmappedBuffer::openBuffer(path, bufOffset, size,
+            isUpdatable);
     if (!mmapedBuffer) {
         return 0;
     }
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.h b/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.h
index 1cb7a89..8cebc3b 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/dictionary_structure_with_buffer_policy_factory.h
@@ -27,8 +27,7 @@
 class DictionaryStructureWithBufferPolicyFactory {
  public:
     static DictionaryStructureWithBufferPolicy *newDictionaryStructureWithBufferPolicy(
-            const char *const path, const int pathLength, const int bufOffset, const int size,
-            const bool isUpdatable);
+            const char *const path, const int bufOffset, const int size, const bool isUpdatable);
 
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(DictionaryStructureWithBufferPolicyFactory);
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp
index cccc090..3cfbfd8 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.cpp
@@ -243,4 +243,29 @@
     return writingHelper.removeBigramWords(word0Pos, word1Pos);
 }
 
+void DynamicPatriciaTriePolicy::flush(const char *const filePath) {
+    if (!mBuffer->isUpdatable()) {
+        AKLOGI("Warning: flush() is called for non-updatable dictionary.");
+        return;
+    }
+    // TODO: Implement.
+}
+
+void DynamicPatriciaTriePolicy::flushWithGC(const char *const filePath) {
+    if (!mBuffer->isUpdatable()) {
+        AKLOGI("Warning: flushWithGC() is called for non-updatable dictionary.");
+        return;
+    }
+    // TODO: Implement.
+}
+
+bool DynamicPatriciaTriePolicy::needsToRunGC() const {
+    if (!mBuffer->isUpdatable()) {
+        AKLOGI("Warning: needsToRunGC() is called for non-updatable dictionary.");
+        return false;
+    }
+    // TODO: Implement.
+    return false;
+}
+
 } // namespace latinime
diff --git a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
index 50c7240..2cbb0ff 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/dynamic_patricia_trie_policy.h
@@ -85,6 +85,12 @@
     bool removeBigramWords(const int *const word0, const int length0, const int *const word1,
             const int length1);
 
+    void flush(const char *const filePath);
+
+    void flushWithGC(const char *const filePath);
+
+    bool needsToRunGC() const;
+
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(DynamicPatriciaTriePolicy);
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.h b/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.h
index 75d9762..cee3e4a 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/patricia_trie_policy.h
@@ -96,6 +96,22 @@
         return false;
     }
 
+    void flush(const char *const filePath) {
+        // This method should not be called for non-updatable dictionary.
+        AKLOGI("Warning: flush() is called for non-updatable dictionary.");
+    }
+
+    void flushWithGC(const char *const filePath) {
+        // This method should not be called for non-updatable dictionary.
+        AKLOGI("Warning: flushWithGC() is called for non-updatable dictionary.");
+    }
+
+    bool needsToRunGC() const {
+        // This method should not be called for non-updatable dictionary.
+        AKLOGI("Warning: needsToRunGC() is called for non-updatable dictionary.");
+        return false;
+    }
+
  private:
     DISALLOW_IMPLICIT_CONSTRUCTORS(PatriciaTriePolicy);
 
diff --git a/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.h b/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.h
index 6febd78..6b69116 100644
--- a/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.h
+++ b/native/jni/src/suggest/policyimpl/dictionary/utils/mmapped_buffer.h
@@ -29,8 +29,8 @@
 
 class MmappedBuffer {
  public:
-    static MmappedBuffer* openBuffer(const char *const path, const int pathLength,
-            const int bufferOffset, const int bufferSize, const bool isUpdatable) {
+    static MmappedBuffer* openBuffer(const char *const path, const int bufferOffset,
+            const int bufferSize, const bool isUpdatable) {
         const int openMode = isUpdatable ? O_RDWR : O_RDONLY;
         const int mmapFd = open(path, openMode);
         if (mmapFd < 0) {