public void clearMemory() {
        // Engine asserts this anyway when removing resources, fail faster and consistently
        Util.assertMainThread();
        // memory cache needs to be cleared before bitmap pool to clear re-pooled Bitmaps too. See #687.
        memoryCache.clearMemory();
        bitmapPool.clearMemory();
    }
Clears as much memory as possible.

@see android.content.ComponentCallbacks#onLowMemory()
@see android.content.ComponentCallbacks2#onLowMemory()
core/src/main/java/com/bumptech/glide/Glide.java