Review comments:

rename empty instances, update page cache eviction tests,
fix eviction boundaries check, cleanup CC version tracker test.

community/consistency-check/src/main/java/org/neo4j/consistency/ConsistencyCheckService.java

@@ -151,7 +151,7 @@ public Result runFullConsistencyCheck( File storeDir, Config config, ProgressMon
         Log log = logProvider.getLog( getClass() );
         ConfiguringPageCacheFactory pageCacheFactory = new ConfiguringPageCacheFactory(
                 fileSystem, config, PageCacheTracer.NULL, PageCursorTracerSupplier.NULL,
-                logProvider.getLog( PageCache.class ), EmptyVersionContextSupplier.INSTANCE );
+                logProvider.getLog( PageCache.class ), EmptyVersionContextSupplier.EMPTY );
         PageCache pageCache = pageCacheFactory.getOrCreatePageCache();
 
         try
@@ -210,7 +210,7 @@ public Result runFullConsistencyCheck( final File storeDir, Config config, Progr
         config.augment( GraphDatabaseSettings.read_only, TRUE );
 
         StoreFactory factory = new StoreFactory( storeDir, config,
-                new DefaultIdGeneratorFactory( fileSystem ), pageCache, fileSystem, logProvider, EmptyVersionContextSupplier.INSTANCE );
+                new DefaultIdGeneratorFactory( fileSystem ), pageCache, fileSystem, logProvider, EmptyVersionContextSupplier.EMPTY );
 
         ConsistencySummaryStatistics summary;
         final File reportFile = chooseReportPath( reportDir );

community/consistency-check/src/test/java/org/neo4j/consistency/checking/GraphStoreFixture.java

@@ -167,7 +167,7 @@ public DirectStoreAccess directStoreAccess()
             Config config = Config.defaults();
             DefaultIdGeneratorFactory idGeneratorFactory = new DefaultIdGeneratorFactory( fileSystem );
             StoreFactory storeFactory = new StoreFactory(
-                    directory, config, idGeneratorFactory, pageCache, fileSystem, logProvider, EmptyVersionContextSupplier.INSTANCE );
+                    directory, config, idGeneratorFactory, pageCache, fileSystem, logProvider, EmptyVersionContextSupplier.EMPTY );
             neoStore = storeFactory.openAllNeoStores();
             StoreAccess nativeStores;
             if ( keepStatistics )

community/consistency-check/src/test/java/org/neo4j/consistency/checking/full/DetectAllRelationshipInconsistenciesIT.java

@@ -151,7 +151,7 @@ private StoreFactory newStoreFactory( PageCache pageCache )
         FileSystemAbstraction fileSystem = fileSystemRule.get();
         return new StoreFactory( directory.directory(), getTuningConfiguration(),
                 new DefaultIdGeneratorFactory( fileSystem ), pageCache, fileSystem, NullLogProvider.getInstance(),
-                EmptyVersionContextSupplier.INSTANCE );
+                EmptyVersionContextSupplier.EMPTY );
     }
 
     private Config getTuningConfiguration()

community/cypher/cypher/src/test/scala/org/neo4j/cypher/internal/spi/v3_3/TransactionBoundQueryContextTest.scala

@@ -67,7 +67,7 @@ class TransactionBoundQueryContextTest extends CypherFunSuite {
     val storeStatement = mock[StorageStatement]
     val operations = mock[StatementOperationParts](RETURNS_DEEP_STUBS)
     statement = new KernelStatement(kernelTransaction, null, storeStatement, new Procedures(), new CanWrite(),
-      LockTracer.NONE, operations, EmptyVersionContextSupplier.INSTANCE)
+      LockTracer.NONE, operations, EmptyVersionContextSupplier.EMPTY)
     statement.initialize(null, PageCursorTracerSupplier.NULL.get())
     statement.acquire()
   }

community/index/src/main/java/org/neo4j/index/internal/gbptree/TreePrinter.java

@@ -76,7 +76,7 @@ public static void printHeader( FileSystemAbstraction fs, File file, PrintStream
         SingleFilePageSwapperFactory swapper = new SingleFilePageSwapperFactory();
         swapper.open( fs, EMPTY );
         try ( PageCache pageCache = new MuninnPageCache( swapper, 100, (int) kibiBytes( 8 ), NULL,
-                PageCursorTracerSupplier.NULL, EmptyVersionContextSupplier.INSTANCE ) )
+                PageCursorTracerSupplier.NULL, EmptyVersionContextSupplier.EMPTY ) )
         {
             printHeader( pageCache, file, out );
         }

community/index/src/test/java/org/neo4j/index/internal/gbptree/GBPTreePartialCreateFuzzIT.java

@@ -105,7 +105,7 @@ public static void main( String[] args ) throws IOException
             SingleFilePageSwapperFactory swapper = new SingleFilePageSwapperFactory();
             swapper.open( fs, EMPTY );
             try ( PageCache pageCache = new MuninnPageCache( swapper, 10, (int) kibiBytes( 8 ),
-                      PageCacheTracer.NULL, PageCursorTracerSupplier.NULL, EmptyVersionContextSupplier.INSTANCE ) )
+                      PageCacheTracer.NULL, PageCursorTracerSupplier.NULL, EmptyVersionContextSupplier.EMPTY ) )
             {
                 fs.deleteFile( file );
                 new GBPTreeBuilder<>( pageCache, file, new SimpleLongLayout() ).build().close();

community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/MuninnPageCache.java

@@ -894,7 +894,7 @@ private void addFreePageToFreelist( long pageRef )
         do
         {
             current = getFreelistHead();
-            if ( current instanceof AtomicInteger && ((AtomicInteger) current).get() >= pages.getPageCount() )
+            if ( current instanceof AtomicInteger && ((AtomicInteger) current).get() > pages.getPageCount() )
             {
                 current = null;
             }

community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/StandalonePageCacheFactory.java

@@ -46,13 +46,13 @@ private StandalonePageCacheFactory()
     public static PageCache createPageCache( FileSystemAbstraction fileSystem )
     {
         return createPageCache( fileSystem, null, PageCacheTracer.NULL, DefaultPageCursorTracerSupplier.INSTANCE,
-                EmptyVersionContextSupplier.INSTANCE );
+                EmptyVersionContextSupplier.EMPTY );
     }
 
     public static PageCache createPageCache( FileSystemAbstraction fileSystem, Integer pageSize )
     {
         return createPageCache( fileSystem, pageSize, PageCacheTracer.NULL, DefaultPageCursorTracerSupplier.INSTANCE,
-                EmptyVersionContextSupplier.INSTANCE );
+                EmptyVersionContextSupplier.EMPTY );
     }
 
     public static PageCache createPageCache( FileSystemAbstraction fileSystem, Integer pageSize,

community/io/src/main/java/org/neo4j/io/pagecache/impl/muninn/SwapperSet.java

@@ -26,9 +26,9 @@
 import org.neo4j.collection.primitive.Primitive;
 import org.neo4j.collection.primitive.PrimitiveIntIterator;
 import org.neo4j.collection.primitive.PrimitiveIntSet;
-import org.neo4j.helpers.Numbers;
 import org.neo4j.io.pagecache.PageSwapper;
 
+import static org.neo4j.helpers.Numbers.safeCastIntToShort;
 import static org.neo4j.helpers.Numbers.safeCastLongToShort;
 
 /**
@@ -101,7 +101,7 @@ synchronized short allocate( PageSwapper swapper )
         {
             if ( !free.isEmpty() )
             {
-                short id = Numbers.safeCastIntToShort( free.iterator().next() );
+                short id = safeCastIntToShort( free.iterator().next() );
                 free.remove( id );
                 swapperMappings[id] = new SwapperMapping( id, swapper );
                 this.swapperMappings = swapperMappings; // Volatile store synchronizes-with loads in getters.

community/io/src/main/java/org/neo4j/io/pagecache/tracing/cursor/context/EmptyVersionContext.java

@@ -25,7 +25,7 @@
  */
 public class EmptyVersionContext implements VersionContext
 {
-    public static final VersionContext INSTANCE = new EmptyVersionContext();
+    public static final VersionContext EMPTY = new EmptyVersionContext();
 
     private EmptyVersionContext()
     {

community/io/src/main/java/org/neo4j/io/pagecache/tracing/cursor/context/EmptyVersionContextSupplier.java

@@ -27,7 +27,7 @@
  */
 public class EmptyVersionContextSupplier implements VersionContextSupplier
 {
-    public static final VersionContextSupplier INSTANCE = new EmptyVersionContextSupplier();
+    public static final VersionContextSupplier EMPTY = new EmptyVersionContextSupplier();
 
     private EmptyVersionContextSupplier()
     {
@@ -41,6 +41,6 @@ public void init( LongSupplier lastClosedTransactionIdSupplier )
     @Override
     public VersionContext getVersionContext()
     {
-        return EmptyVersionContext.INSTANCE;
+        return EmptyVersionContext.EMPTY;
     }
 }

community/io/src/test/java/org/neo4j/io/pagecache/PageCacheTestSupport.java

@@ -114,7 +114,7 @@ protected final T createPageCache( PageSwapperFactory swapperFactory, int maxPag
             PageCacheTracer tracer, PageCursorTracerSupplier cursorTracerSupplier )
     {
         return createPageCache( swapperFactory, maxPages, pageSize, tracer, cursorTracerSupplier,
-                EmptyVersionContextSupplier.INSTANCE );
+                EmptyVersionContextSupplier.EMPTY );
     }
 
     protected final T createPageCache( PageSwapperFactory swapperFactory, int maxPages, int pageSize,
@@ -128,7 +128,7 @@ protected T createPageCache( FileSystemAbstraction fs, int maxPages, int pageSiz
             PageCursorTracerSupplier cursorTracerSupplier )
     {
         return createPageCache( fs, maxPages, pageSize, tracer, cursorTracerSupplier,
-                EmptyVersionContextSupplier.INSTANCE );
+                EmptyVersionContextSupplier.EMPTY );
     }
 
     protected T createPageCache( FileSystemAbstraction fs, int maxPages, int pageSize, PageCacheTracer tracer,

community/io/src/test/java/org/neo4j/io/pagecache/impl/muninn/MuninnPageCacheTest.java

@@ -42,7 +42,6 @@
 import org.neo4j.io.pagecache.tracing.EvictionRunEvent;
 import org.neo4j.io.pagecache.tracing.MajorFlushEvent;
 import org.neo4j.io.pagecache.tracing.PageCacheTracer;
-import org.neo4j.io.pagecache.tracing.PageFaultEvent;
 import org.neo4j.io.pagecache.tracing.cursor.DefaultPageCursorTracerSupplier;
 import org.neo4j.io.pagecache.tracing.cursor.PageCursorTracerSupplier;
 import org.neo4j.io.pagecache.tracing.cursor.context.VersionContext;
@@ -95,6 +94,28 @@ public MajorFlushEvent beginCacheFlush()
         };
     }
 
+    @Test
+    public void ableToEvictAllPageInAPageCache() throws IOException
+    {
+        writeInitialDataTo( file( "a" ) );
+        RecordingPageCacheTracer tracer = new RecordingPageCacheTracer();
+        RecordingPageCursorTracer cursorTracer = new RecordingPageCursorTracer();
+        ConfigurablePageCursorTracerSupplier cursorTracerSupplier = new ConfigurablePageCursorTracerSupplier( cursorTracer );
+        try ( MuninnPageCache pageCache = createPageCache( fs, 2, 8, blockCacheFlush( tracer ), cursorTracerSupplier );
+                PagedFile pagedFile = pageCache.map( file( "a" ), 8 ) )
+        {
+            try ( PageCursor cursor = pagedFile.io( 0, PF_SHARED_READ_LOCK ) )
+            {
+                assertTrue( cursor.next() );
+            }
+            try ( PageCursor cursor = pagedFile.io( 1, PF_SHARED_READ_LOCK ) )
+            {
+                assertTrue( cursor.next() );
+            }
+            assertEquals( 2, pageCache.evictPages( 2, 0, EvictionRunEvent.NULL ) );
+        }
+    }
+
     @Test
     public void mustEvictCleanPageWithoutFlushing() throws Exception
     {
@@ -414,8 +435,7 @@ public void markContextAsDirtyWhenAnyEvictedPageHaveModificationTransactionHighe
             cursor.putLong( 4 );
         }
 
-        pageCache.pages.tryEvict( pageCache.grabFreeAndExclusivelyLockedPage( PageFaultEvent.NULL ),
-                EvictionRunEvent.NULL );
+        assertEquals( 2, pageCache.evictPages( 2, 0, EvictionRunEvent.NULL ) );
 
         cursorContext.initRead();
         try ( PageCursor cursor = pagedFile.io( 0, PF_SHARED_READ_LOCK ) )
@@ -449,8 +469,7 @@ public void doNotMarkContextAsDirtyWhenAnyEvictedPageHaveModificationTransaction
             cursor.putLong( 4 );
         }
 
-        pageCache.pages.tryEvict( pageCache.grabFreeAndExclusivelyLockedPage( PageFaultEvent.NULL ),
-                EvictionRunEvent.NULL );
+        assertEquals( 2, pageCache.evictPages( 2, 0, EvictionRunEvent.NULL ) );
 
         cursorContext.initRead();
         try ( PageCursor cursor = pagedFile.io( 0, PF_SHARED_READ_LOCK ) )

community/io/src/test/java/org/neo4j/io/pagecache/randomharness/RandomPageCacheTestHarness.java

@@ -386,7 +386,7 @@ private void runIteration( long timeout, TimeUnit unit ) throws Exception
         PageSwapperFactory swapperFactory = new SingleFilePageSwapperFactory();
         swapperFactory.open( fs, Configuration.EMPTY );
         MuninnPageCache cache = new MuninnPageCache( swapperFactory, cachePageCount, cachePageSize, tracer,
-                cursorTracerSupplier, EmptyVersionContextSupplier.INSTANCE );
+                cursorTracerSupplier, EmptyVersionContextSupplier.EMPTY );
         cache.setPrintExceptionsOnClose( false );
         Map<File,PagedFile> fileMap = new HashMap<>( files.length );
         for ( int i = 0; i < Math.min( files.length, initialMappedFiles ); i++ )

community/io/src/test/java/org/neo4j/io/pagecache/stress/PageCacheStressTest.java

@@ -92,7 +92,7 @@ public void run() throws Exception
             swapperFactory.open( fs, Configuration.EMPTY );
 
             try ( PageCache pageCacheUnderTest = new MuninnPageCache( swapperFactory, numberOfCachePages, cachePageSize,
-                    tracer, pageCursorTracerSupplier, EmptyVersionContextSupplier.INSTANCE ) )
+                    tracer, pageCursorTracerSupplier, EmptyVersionContextSupplier.EMPTY ) )
             {
                 PageCacheStresser pageCacheStresser =
                         new PageCacheStresser( numberOfPages, numberOfThreads, workingDirectory );

community/io/src/test/java/org/neo4j/test/rule/PageCacheRule.java

@@ -173,7 +173,7 @@ public PageCache getPageCache( FileSystemAbstraction fs, PageCacheConfig overrid
                 selectConfig( baseConfig.pageSize, overriddenConfig.pageSize, null ),
                 selectConfig( baseConfig.tracer, overriddenConfig.tracer, PageCacheTracer.NULL ),
                 selectConfig( baseConfig.pageCursorTracerSupplier, overriddenConfig.pageCursorTracerSupplier,
-                        DefaultPageCursorTracerSupplier.INSTANCE ), EmptyVersionContextSupplier.INSTANCE);
+                        DefaultPageCursorTracerSupplier.INSTANCE ), EmptyVersionContextSupplier.EMPTY );
         pageCachePostConstruct( overriddenConfig );
         return pageCache;
     }

community/kernel/src/main/java/org/neo4j/kernel/impl/api/TransactionToApply.java

@@ -81,7 +81,7 @@ public class TransactionToApply implements CommandsToApply, AutoCloseable
      */
     public TransactionToApply( TransactionRepresentation transactionRepresentation )
     {
-        this( transactionRepresentation, EmptyVersionContext.INSTANCE );
+        this( transactionRepresentation, EmptyVersionContext.EMPTY );
     }
 
     /**
@@ -94,7 +94,7 @@ public TransactionToApply( TransactionRepresentation transactionRepresentation,
 
     public TransactionToApply( TransactionRepresentation transactionRepresentation, long transactionId )
     {
-        this( transactionRepresentation, transactionId, EmptyVersionContext.INSTANCE );
+        this( transactionRepresentation, transactionId, EmptyVersionContext.EMPTY );
     }
 
     public TransactionToApply( TransactionRepresentation transactionRepresentation, long transactionId,

community/kernel/src/main/java/org/neo4j/kernel/impl/context/TransactionVersionContextSupplier.java

@@ -42,7 +42,7 @@ public void init( LongSupplier lastClosedTransactionIdSupplier )
     @Override
     public VersionContext getVersionContext()
     {
-        return cursorContext == null ? EmptyVersionContext.INSTANCE : cursorContext.get();
+        return cursorContext == null ? EmptyVersionContext.EMPTY : cursorContext.get();
     }
 
 }

community/kernel/src/main/java/org/neo4j/kernel/impl/factory/PlatformModule.java

@@ -214,7 +214,7 @@ public PlatformModule( File providedStoreDir, Config config, DatabaseInfo databa
     protected VersionContextSupplier createCursorContextSupplier( Config config )
     {
         return config.get( GraphDatabaseSettings.snapshot_query ) ? new TransactionVersionContextSupplier()
-                                                                  : EmptyVersionContextSupplier.INSTANCE;
+                                                                  : EmptyVersionContextSupplier.EMPTY;
     }
 
     protected AvailabilityGuard createAvailabilityGuard()

community/kernel/src/main/java/org/neo4j/kernel/impl/pagecache/ConfigurableStandalonePageCacheFactory.java

@@ -48,13 +48,13 @@ private ConfigurableStandalonePageCacheFactory()
     public static PageCache createPageCache( FileSystemAbstraction fileSystem )
     {
         return createPageCache( fileSystem, PageCacheTracer.NULL, DefaultPageCursorTracerSupplier.INSTANCE,
-                Config.defaults(), EmptyVersionContextSupplier.INSTANCE );
+                Config.defaults(), EmptyVersionContextSupplier.EMPTY );
     }
 
     public static PageCache createPageCache( FileSystemAbstraction fileSystem, Config config )
     {
         return createPageCache( fileSystem, PageCacheTracer.NULL, DefaultPageCursorTracerSupplier.INSTANCE, config,
-                EmptyVersionContextSupplier.INSTANCE );
+                EmptyVersionContextSupplier.EMPTY );
     }
 
     /**

community/kernel/src/main/java/org/neo4j/kernel/impl/store/StoreAccess.java

@@ -76,7 +76,7 @@ public StoreAccess( NeoStores store )
     public StoreAccess( FileSystemAbstraction fileSystem, PageCache pageCache, File storeDir, Config config )
     {
         this( new StoreFactory( storeDir, config, new DefaultIdGeneratorFactory( fileSystem ), pageCache,
-                fileSystem, NullLogProvider.getInstance(), EmptyVersionContextSupplier.INSTANCE ).openAllNeoStores() );
+                fileSystem, NullLogProvider.getInstance(), EmptyVersionContextSupplier.EMPTY ).openAllNeoStores() );
         this.closeable = true;
     }
 

community/kernel/src/main/java/org/neo4j/kernel/impl/store/counts/ReadOnlyCountsTracker.java

@@ -35,7 +35,7 @@ public class ReadOnlyCountsTracker extends CountsTracker
     public ReadOnlyCountsTracker( LogProvider logProvider, FileSystemAbstraction fileSystem, PageCache pageCache,
                                   Config config, File baseFile )
     {
-        super( logProvider, fileSystem, pageCache, config, baseFile, EmptyVersionContextSupplier.INSTANCE );
+        super( logProvider, fileSystem, pageCache, config, baseFile, EmptyVersionContextSupplier.EMPTY );
     }
 
     @Override

community/kernel/src/main/java/org/neo4j/kernel/impl/store/kvstore/State.java

@@ -51,7 +51,7 @@ public <Key> ActiveState<Key> open( ReadableState<Key> store, File file, Version
             @Override
             public <Key> ActiveState<Key> open( ReadableState<Key> store, File file, VersionContextSupplier versionContextSupplier )
             {
-                return new ConcurrentMapState<Key>( store, file, EmptyVersionContextSupplier.INSTANCE )
+                return new ConcurrentMapState<Key>( store, file, EmptyVersionContextSupplier.EMPTY )
                 {
                     @Override
                     protected boolean hasChanges()

community/kernel/src/main/java/org/neo4j/kernel/impl/storemigration/DirectRecordStoreMigrator.java

@@ -66,11 +66,11 @@ public void migrate( File fromStoreDir, RecordFormats fromFormat, File toStoreDi
 
         try (
                 NeoStores fromStores = new StoreFactory( fromStoreDir, config, new DefaultIdGeneratorFactory( fs ),
-                    pageCache, fs, fromFormat, NullLogProvider.getInstance(), EmptyVersionContextSupplier.INSTANCE )
+                    pageCache, fs, fromFormat, NullLogProvider.getInstance(), EmptyVersionContextSupplier.EMPTY )
                         .openNeoStores( true, storesToOpen );
                 NeoStores toStores = new StoreFactory( toStoreDir, withPersistedStoreHeadersAsConfigFrom( fromStores, storesToOpen ),
                     new DefaultIdGeneratorFactory( fs ), pageCache, fs, toFormat, NullLogProvider.getInstance(),
-                        EmptyVersionContextSupplier.INSTANCE )
+                        EmptyVersionContextSupplier.EMPTY )
                         .openNeoStores( true, storesToOpen ) )
         {
             for ( StoreType type : types )

community/kernel/src/main/java/org/neo4j/kernel/impl/storemigration/participant/CountsMigrator.java

@@ -159,7 +159,7 @@ private void rebuildCountsFromScratch( File storeDirToReadFrom, File migrationDi
         RecordFormats recordFormats = selectForVersion( expectedStoreVersion );
         IdGeneratorFactory idGeneratorFactory = new ReadOnlyIdGeneratorFactory( fileSystem );
         StoreFactory storeFactory = new StoreFactory( storeDirToReadFrom, config, idGeneratorFactory, pageCache,
-                fileSystem, recordFormats, logProvider, EmptyVersionContextSupplier.INSTANCE );
+                fileSystem, recordFormats, logProvider, EmptyVersionContextSupplier.EMPTY );
         try ( NeoStores neoStores = storeFactory
                 .openNeoStores( StoreType.NODE, StoreType.RELATIONSHIP, StoreType.LABEL_TOKEN,
                         StoreType.RELATIONSHIP_TYPE_TOKEN ) )
@@ -175,7 +175,7 @@ private void rebuildCountsFromScratch( File storeDirToReadFrom, File migrationDi
                         highRelationshipTypeId, NumberArrayFactory.auto( pageCache, migrationDir, true ),
                         progressMonitor );
                 life.add( new CountsTracker( logProvider, fileSystem, pageCache, config,
-                        storeFileBase, EmptyVersionContextSupplier.INSTANCE ).setInitializer( initializer ) );
+                        storeFileBase, EmptyVersionContextSupplier.EMPTY ).setInitializer( initializer ) );
             }
         }
     }

community/kernel/src/main/java/org/neo4j/kernel/impl/storemigration/participant/NativeLabelScanStoreMigrator.java

@@ -141,7 +141,7 @@ private StoreFactory getStoreFactory( File storeDir, String versionToMigrateFrom
         RecordFormats recordFormats = selectForVersion( versionToMigrateFrom );
         IdGeneratorFactory idGeneratorFactory = new ReadOnlyIdGeneratorFactory( fileSystem );
         return new StoreFactory( storeDir, config, idGeneratorFactory, pageCache, fileSystem,
-                recordFormats, logProvider, EmptyVersionContextSupplier.INSTANCE );
+                recordFormats, logProvider, EmptyVersionContextSupplier.EMPTY );
     }
 
     private boolean isNativeLabelScanStoreMigrationRequired( File storeDir ) throws IOException