Merge pull request #154 from Zor-X-L/fallocate

try to preallocate space after RandomAccessFile#setLength()

src/main/java/net/openhft/chronicle/hash/impl/VanillaChronicleHash.java

@@ -26,6 +26,7 @@ import net.openhft.chronicle.hash.*;
 import net.openhft.chronicle.hash.impl.util.BuildVersion;
 import net.openhft.chronicle.hash.impl.util.Cleaner;
 import net.openhft.chronicle.hash.impl.util.CleanerUtils;
+import net.openhft.chronicle.hash.impl.util.jna.PosixFallocate;
 import net.openhft.chronicle.hash.impl.util.jna.PosixMsync;
 import net.openhft.chronicle.hash.impl.util.jna.WindowsMsync;
 import net.openhft.chronicle.hash.serialization.DataAccess;
@@ -40,10 +41,7 @@ import net.openhft.chronicle.wire.WireIn;
 import net.openhft.chronicle.wire.WireOut;
 import org.jetbrains.annotations.NotNull;
 
-import java.io.Closeable;
-import java.io.File;
-import java.io.IOException;
-import java.io.RandomAccessFile;
+import java.io.*;
 import java.lang.ref.WeakReference;
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
@@ -957,6 +955,16 @@ public abstract class VanillaChronicleHash<K,
             // globalMutableStateLock), or on map creation, when race condition should be excluded
             // by self-bootstrapping header spec
             raf.setLength(minFileSize);
+
+            // RandomAccessFile#setLength() only calls ftruncate,
+            // which will not preallocate space on XFS filesystem of Linux.
+            // And writing that file will create a sparse file with a large number of extents.
+            // This kind of fragmented file may hang the program and cause dmesg reports
+            // "XFS: ... possible memory allocation deadlock size ... in kmem_alloc (mode:0x250)".
+            // We can fix this by trying calling posix_fallocate to preallocate the space.
+            if (OS.isLinux()) {
+                PosixFallocate.fallocate(raf.getFD(), 0, minFileSize);
+            }
         }
         long address = OS.map(fileChannel, READ_WRITE, mappingOffsetInFile, mapSize);
         resources.addMemoryResource(address, mapSize);

src/main/java/net/openhft/chronicle/hash/impl/util/jna/PosixFallocate.java

@@ -0,0 +1,46 @@
+package net.openhft.chronicle.hash.impl.util.jna;
+
+import com.sun.jna.Native;
+import com.sun.jna.Platform;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.FileDescriptor;
+import java.lang.reflect.Field;
+
+public final class PosixFallocate {
+
+    private static final Logger LOG =
+            LoggerFactory.getLogger(PosixFallocate.class.getName());
+
+    static {
+        Native.register(Platform.C_LIBRARY_NAME);
+    }
+
+    private PosixFallocate() {
+    }
+
+    public static void fallocate(FileDescriptor descriptor, long offset, long length) {
+        int fd = getNativeFileDescriptor(descriptor);
+        if (fd != -1) {
+            int ret = posix_fallocate(getNativeFileDescriptor(descriptor), offset, length);
+            if (ret != 0) {
+                LOG.warn("posix_fallocate() returned {}", ret);
+            }
+        }
+    }
+
+    private static native int posix_fallocate(int fd, long offset, long length);
+
+    private static int getNativeFileDescriptor(FileDescriptor descriptor) {
+        try {
+            final Field field = descriptor.getClass().getDeclaredField("fd");
+            field.setAccessible(true);
+            return (int) field.get(descriptor);
+        } catch (final Exception e) {
+            LOG.warn("unsupported FileDescriptor implementation: e={}", e.getLocalizedMessage());
+            return -1;
+        }
+    }
+
+}