Log a warning on badly balanced page cache configurations

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

@@ -76,7 +76,7 @@ public Result runFullConsistencyCheck( File storeDir,
         Log log = logProvider.getLog( getClass() );
         DefaultFileSystemAbstraction fileSystem = new DefaultFileSystemAbstraction();
         ConfiguringPageCacheFactory pageCacheFactory = new ConfiguringPageCacheFactory(
-                fileSystem, tuningConfiguration, PageCacheTracer.NULL );
+                fileSystem, tuningConfiguration, PageCacheTracer.NULL, logProvider.getLog( PageCache.class ) );
         PageCache pageCache = pageCacheFactory.getOrCreatePageCache();
 
         try

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

@@ -55,6 +55,7 @@
 import org.neo4j.kernel.lifecycle.LifeSupport;
 import org.neo4j.kernel.monitoring.Monitors;
 import org.neo4j.kernel.monitoring.tracing.Tracers;
+import org.neo4j.logging.Log;
 import org.neo4j.logging.LogProvider;
 import org.neo4j.logging.NullLogProvider;
 
@@ -224,13 +225,14 @@ protected Neo4jJobScheduler createJobScheduler()
 
     protected PageCache createPageCache( FileSystemAbstraction fileSystem, Config config, LogService logging, Tracers tracers)
     {
+        Log pageCacheLog = logging.getInternalLog( PageCache.class );
         ConfiguringPageCacheFactory pageCacheFactory = new ConfiguringPageCacheFactory(
-                fileSystem, config, tracers.pageCacheTracer );
+                fileSystem, config, tracers.pageCacheTracer, pageCacheLog );
         PageCache pageCache = pageCacheFactory.getOrCreatePageCache();
 
         if ( config.get( GraphDatabaseSettings.dump_configuration ) )
         {
-            pageCacheFactory.dumpConfiguration( logging.getInternalLog( PageCache.class ) );
+            pageCacheFactory.dumpConfiguration();
         }
         return pageCache;
     }

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

@@ -39,14 +39,16 @@ public class ConfiguringPageCacheFactory
     private final PageSwapperFactory swapperFactory;
     private final Config config;
     private final PageCacheTracer tracer;
+    private final Log log;
     private PageCache pageCache;
 
     public ConfiguringPageCacheFactory(
-            FileSystemAbstraction fs, Config config, PageCacheTracer tracer )
+            FileSystemAbstraction fs, Config config, PageCacheTracer tracer, Log log )
     {
         this.swapperFactory = new SingleFilePageSwapperFactory( fs );
         this.config = config;
         this.tracer = tracer;
+        this.log = log;
     }
 
     public synchronized PageCache getOrCreatePageCache()
@@ -69,18 +71,25 @@ protected PageCache createPageCache()
 
     public int calculateMaxPages( Config config )
     {
-        long availableMemory = config.get( pagecache_memory );
+        long pageCacheMemory = config.get( pagecache_memory );
+        long maxHeap = Runtime.getRuntime().maxMemory();
+        if ( pageCacheMemory / maxHeap > 100 )
+        {
+            log.warn( "The memory configuration looks unbalanced. It is generally recommended to have at least " +
+                      "10 KiB of heap memory, for every 1 MiB of page cache memory. The current configuration is " +
+                      "allocating %s bytes for the page cache, and %s bytes for the heap.", pageCacheMemory, maxHeap );
+        }
         long pageSize = config.get( mapped_memory_page_size );
-        long pageCount = availableMemory / pageSize;
-        return (int) Math.min( Integer.MAX_VALUE, pageCount );
+        long pageCount = pageCacheMemory / pageSize;
+        return (int) Math.min( Integer.MAX_VALUE - 2000, pageCount );
     }
 
     public int calculatePageSize( Config config )
     {
         return config.get( mapped_memory_page_size ).intValue();
     }
 
-    public void dumpConfiguration( Log log )
+    public void dumpConfiguration()
     {
         long totalPhysicalMemory = totalPhysicalMemory();
         String totalPhysicalMemMb = totalPhysicalMemory == -1? "?" : "" + totalPhysicalMemory / 1024 / 1024;

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

@@ -25,6 +25,7 @@
 import org.neo4j.io.pagecache.PageCache;
 import org.neo4j.io.pagecache.tracing.PageCacheTracer;
 import org.neo4j.kernel.configuration.Config;
+import org.neo4j.logging.FormattedLogProvider;
 
 /*
  * This class is an helper to allow to construct properly a page cache in the few places we need it without all
@@ -51,8 +52,9 @@ public static PageCache createPageCache(
         Config baseConfig = new Config( MapUtil.stringMap(
                 GraphDatabaseSettings.pagecache_memory.name(), "8M" ) );
         Config finalConfig = baseConfig.with( config.getParams() );
+        FormattedLogProvider logProvider = FormattedLogProvider.toOutputStream( System.err );
         ConfiguringPageCacheFactory pageCacheFactory = new ConfiguringPageCacheFactory(
-                fileSystem, finalConfig, PageCacheTracer.NULL );
+                fileSystem, finalConfig, PageCacheTracer.NULL, logProvider.getLog( PageCache.class ) );
         return pageCacheFactory.getOrCreatePageCache();
     }
 }

community/kernel/src/main/java/org/neo4j/unsafe/batchinsert/BatchInserterImpl.java

@@ -134,6 +134,7 @@
 import org.neo4j.kernel.impl.util.Neo4jJobScheduler;
 import org.neo4j.kernel.lifecycle.LifeSupport;
 import org.neo4j.logging.Log;
+import org.neo4j.logging.NullLog;
 import org.neo4j.logging.NullLogProvider;
 import org.neo4j.kernel.monitoring.Monitors;
 
@@ -240,7 +241,7 @@ public Label apply( long from )
         this.fileSystem = fileSystem;
         this.storeDir = storeDir;
         ConfiguringPageCacheFactory pageCacheFactory = new ConfiguringPageCacheFactory(
-                fileSystem, config, PageCacheTracer.NULL );
+                fileSystem, config, PageCacheTracer.NULL, NullLog.getInstance() );
         PageCache pageCache = pageCacheFactory.getOrCreatePageCache();
 
         JobScheduler jobScheduler = life.add( new Neo4jJobScheduler() );

community/kernel/src/test/java/org/neo4j/kernel/impl/pagecache/ConfiguringPageCacheFactoryTest.java

@@ -25,6 +25,7 @@
 import org.neo4j.io.pagecache.PageCache;
 import org.neo4j.io.pagecache.tracing.PageCacheTracer;
 import org.neo4j.kernel.configuration.Config;
+import org.neo4j.logging.NullLog;
 import org.neo4j.test.EphemeralFileSystemRule;
 
 import static org.hamcrest.CoreMatchers.equalTo;
@@ -49,7 +50,7 @@ public void shouldUseConfiguredPageSizeAndFitAsManyPagesAsItCan() throws Throwab
 
         // When
         ConfiguringPageCacheFactory pageCacheFactory = new ConfiguringPageCacheFactory(
-                fsRule.get(), config, PageCacheTracer.NULL );
+                fsRule.get(), config, PageCacheTracer.NULL, NullLog.getInstance() );
         PageCache cache = pageCacheFactory.getOrCreatePageCache();
 
         // Then

enterprise/enterprise-performance-tests/src/main/java/org/neo4j/perftest/enterprise/ccheck/ConsistencyPerformanceCheck.java

@@ -43,6 +43,7 @@
 import org.neo4j.kernel.impl.store.StoreAccess;
 import org.neo4j.kernel.impl.store.StoreFactory;
 import org.neo4j.kernel.monitoring.Monitors;
+import org.neo4j.logging.NullLog;
 import org.neo4j.logging.NullLogProvider;
 import org.neo4j.perftest.enterprise.generator.DataGenerator;
 import org.neo4j.perftest.enterprise.util.Configuration;
@@ -120,7 +121,7 @@ private static void run( Configuration configuration ) throws Exception
         Config tuningConfiguration = buildTuningConfiguration( configuration );
         fileSystem = new DefaultFileSystemAbstraction();
         ConfiguringPageCacheFactory pageCacheFactory = new ConfiguringPageCacheFactory(
-                fileSystem, tuningConfiguration, PageCacheTracer.NULL );
+                fileSystem, tuningConfiguration, PageCacheTracer.NULL, NullLog.getInstance() );
         pageCache = pageCacheFactory.getOrCreatePageCache();
         DirectStoreAccess directStoreAccess = createScannableStores( storeDir, tuningConfiguration );
 

enterprise/enterprise-performance-tests/src/main/java/org/neo4j/perftest/enterprise/generator/DataGenerator.java

@@ -38,6 +38,7 @@
 import org.neo4j.kernel.impl.pagecache.ConfiguringPageCacheFactory;
 import org.neo4j.kernel.impl.store.RecordStore;
 import org.neo4j.kernel.impl.store.StoreAccess;
+import org.neo4j.logging.NullLog;
 import org.neo4j.perftest.enterprise.util.Configuration;
 import org.neo4j.perftest.enterprise.util.Conversion;
 import org.neo4j.perftest.enterprise.util.Parameters;
@@ -121,7 +122,8 @@ public static void run( Configuration configuration ) throws IOException
             batchInserter.shutdown();
         }
         ConfiguringPageCacheFactory pageCacheFactory = new ConfiguringPageCacheFactory(
-                new DefaultFileSystemAbstraction(), new Config( config ), PageCacheTracer.NULL );
+                new DefaultFileSystemAbstraction(), new Config( config ), PageCacheTracer.NULL,
+                NullLog.getInstance() );
         PageCache pageCache = pageCacheFactory.getOrCreatePageCache();
         StoreAccess stores = new StoreAccess( pageCache, storeDir );
         try