extra trickery to avoid one extra copy

dhfs-parent/server/docker-compose.yml

@@ -30,6 +30,7 @@ services:
       - $HOME/dhfs/dhfs2_f:/dhfs_root/fuse:rshared
       - ./target/quarkus-app:/app
     command: "java --add-exports java.base/sun.nio.ch=ALL-UNNAMED
+     --add-exports java.base/jdk.internal.access=ALL-UNNAMED
      -Ddhfs.objects.persistence.files.root=/dhfs_root/p 
      -Ddhfs.objects.root=/dhfs_root/d 
      -Ddhfs.fuse.root=/dhfs_root/fuse -Dquarkus.http.host=0.0.0.0

dhfs-parent/server/pom.xml

@@ -8,7 +8,10 @@
 
     <properties>
         <compiler-plugin.version>3.12.1</compiler-plugin.version>
-        <maven.compiler.release>21</maven.compiler.release>
+        <!--FIXME-->
+        <maven.compiler.release></maven.compiler.release>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
         <quarkus.platform.artifact-id>quarkus-bom</quarkus.platform.artifact-id>
@@ -167,6 +170,8 @@
                 <configuration>
                     <compilerArgs>
                         <arg>-parameters</arg>
+                        <arg>--add-exports</arg>
+                        <arg>java.base/jdk.internal.access=ALL-UNNAMED</arg>
                     </compilerArgs>
                 </configuration>
             </plugin>
@@ -178,7 +183,10 @@
                         <java.util.logging.manager>org.jboss.logmanager.LogManager</java.util.logging.manager>
                         <maven.home>${maven.home}</maven.home>
                     </systemPropertyVariables>
-                    <argLine>--add-exports java.base/sun.nio.ch=ALL-UNNAMED</argLine>
+                    <argLine>
+                        --add-exports java.base/sun.nio.ch=ALL-UNNAMED
+                        --add-exports java.base/jdk.internal.access=ALL-UNNAMED
+                    </argLine>
                     <skipTests>${skip.unit}</skipTests>
                 </configuration>
             </plugin>

dhfs-parent/server/src/main/java/com/usatiuk/dhfs/fuse/DhfsFuse.java

@@ -49,6 +49,9 @@ public class DhfsFuse extends FuseStubFS {
     @ConfigProperty(name = "dhfs.files.target_chunk_size")
     int targetChunkSize;
 
+    @Inject
+    JnrPtrByteOutputAccessors jnrPtrByteOutputAccessors;
+
     @Inject
     DhfsFileService fileService;
 
@@ -166,7 +169,7 @@ public class DhfsFuse extends FuseStubFS {
             var file = fileOpt.get();
             var read = fileService.read(fileOpt.get(), offset, (int) size);
             if (read.isEmpty()) return 0;
-            UnsafeByteOperations.unsafeWriteTo(read.get(), new JnrPtrByteOutput(buf, size));
+            UnsafeByteOperations.unsafeWriteTo(read.get(), new JnrPtrByteOutput(jnrPtrByteOutputAccessors, buf, size));
             return read.get().size();
         } catch (Exception e) {
             Log.error("When reading " + path, e);
@@ -318,7 +321,7 @@ public class DhfsFuse extends FuseStubFS {
             var file = fileOpt.get();
             var read = fileService.readlinkBS(fileOpt.get());
             if (read.isEmpty()) return 0;
-            UnsafeByteOperations.unsafeWriteTo(read, new JnrPtrByteOutput(buf, size));
+            UnsafeByteOperations.unsafeWriteTo(read, new JnrPtrByteOutput(jnrPtrByteOutputAccessors, buf, size));
             buf.putByte(Math.min(size - 1, read.size()), (byte) 0);
             return 0;
         } catch (Exception e) {

dhfs-parent/server/src/main/java/com/usatiuk/dhfs/fuse/JnrPtrByteOutput.java

@@ -9,10 +9,13 @@ public class JnrPtrByteOutput extends ByteOutput {
     private final Pointer _backing;
     private final long _size;
     private long _pos;
-    public JnrPtrByteOutput(Pointer backing, long size) {
+    private final JnrPtrByteOutputAccessors _accessors;
+
+    public JnrPtrByteOutput(JnrPtrByteOutputAccessors accessors, Pointer backing, long size) {
         _backing = backing;
         _size = size;
         _pos = 0;
+        _accessors = accessors;
     }
 
     @Override
@@ -36,11 +39,22 @@ public class JnrPtrByteOutput extends ByteOutput {
 
     @Override
     public void write(ByteBuffer value) {
-        throw new UnsupportedOperationException();
+        var rem = value.remaining();
+        if (rem + _pos > _size) throw new IndexOutOfBoundsException();
+
+        if (value.isDirect()) {
+            long addr = _accessors.getNioAccess().getBufferAddress(value) + value.position();
+            var out = _backing.address() + _pos;
+            _accessors.getUnsafe().copyMemory(addr, out, rem);
+        } else {
+            throw new UnsupportedOperationException();
+        }
+
+        _pos += rem;
     }
 
     @Override
     public void writeLazy(ByteBuffer value) {
-        throw new UnsupportedOperationException();
+        write(value);
     }
 }

dhfs-parent/server/src/main/java/com/usatiuk/dhfs/fuse/JnrPtrByteOutputAccessors.java

@@ -0,0 +1,24 @@
+package com.usatiuk.dhfs.fuse;
+
+import jakarta.inject.Singleton;
+import jdk.internal.access.JavaNioAccess;
+import jdk.internal.access.SharedSecrets;
+import lombok.Getter;
+import sun.misc.Unsafe;
+
+import java.lang.reflect.Field;
+
+@Singleton
+class JnrPtrByteOutputAccessors {
+    @Getter
+    JavaNioAccess _nioAccess;
+    @Getter
+    Unsafe _unsafe;
+
+    JnrPtrByteOutputAccessors() throws NoSuchFieldException, IllegalAccessException {
+        _nioAccess = SharedSecrets.getJavaNioAccess();
+        Field f = Unsafe.class.getDeclaredField("theUnsafe");
+        f.setAccessible(true);
+        _unsafe = (Unsafe) f.get(null);
+    }
+}

dhfs-parent/server/src/main/java/com/usatiuk/dhfs/objects/repository/persistence/FileObjectPersistentStore.java

@@ -1,5 +1,6 @@
 package com.usatiuk.dhfs.objects.repository.persistence;
 
+import com.google.protobuf.CodedOutputStream;
 import com.google.protobuf.Message;
 import com.google.protobuf.UnsafeByteOperations;
 import com.usatiuk.dhfs.objects.persistence.JObjectDataP;
@@ -17,6 +18,7 @@ import org.eclipse.microprofile.config.inject.ConfigProperty;
 
 import javax.annotation.Nonnull;
 import java.io.*;
+import java.nio.channels.FileChannel;
 import java.nio.file.Files;
 import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
@@ -33,6 +35,8 @@ public class FileObjectPersistentStore implements ObjectPersistentStore {
     private final Path metaPath;
     private final Path dataPath;
 
+    private final static long mmapThreshold = 65536;
+
     public FileObjectPersistentStore(@ConfigProperty(name = "dhfs.objects.persistence.files.root") String root) {
         this.root = root;
         this.metaPath = Paths.get(root, "meta");
@@ -108,9 +112,20 @@ public class FileObjectPersistentStore implements ObjectPersistentStore {
     }
 
     private <T extends Message> T readObjectImpl(T defaultInstance, Path path) {
-        try (var fsb = new FileInputStream(path.toFile())) {
-            var file = fsb.readAllBytes();
-            return (T) defaultInstance.getParserForType().parseFrom(UnsafeByteOperations.unsafeWrap(file));
+        try (var rf = new RandomAccessFile(path.toFile(), "r")) {
+            var len = rf.length();
+            if (len > mmapThreshold) {
+                var bs = UnsafeByteOperations.unsafeWrap(rf.getChannel().map(FileChannel.MapMode.READ_ONLY, 0, len));
+                // This way, the input will be considered "immutable" which would allow avoiding copies
+                // when parsing byte arrays
+                var ch = bs.newCodedInput();
+                ch.enableAliasing(true);
+                return (T) defaultInstance.getParserForType().parseFrom(ch);
+            } else {
+                var arr = new byte[(int) len];
+                rf.readFully(arr, 0, (int) len);
+                return (T) defaultInstance.getParserForType().parseFrom(UnsafeByteOperations.unsafeWrap(arr));
+            }
         } catch (FileNotFoundException | NoSuchFileException fx) {
             throw new StatusRuntimeExceptionNoStacktrace(Status.NOT_FOUND);
         } catch (IOException e) {
@@ -133,6 +148,15 @@ public class FileObjectPersistentStore implements ObjectPersistentStore {
 
     private void writeObjectImpl(Path path, Message data) {
         try {
+            var len = data.getSerializedSize();
+            if (len > mmapThreshold)
+                try (var rf = new RandomAccessFile(path.toFile(), "rw")) {
+                    rf.setLength(len);
+                    var mapped = rf.getChannel().map(FileChannel.MapMode.READ_WRITE, 0, len);
+                    data.writeTo(CodedOutputStream.newInstance(mapped));
+                    return;
+                }
+
             try (var fsb = new FileOutputStream(path.toFile(), false);
                  var buf = new BufferedOutputStream(fsb, Math.min(65536, data.getSerializedSize()))) {
                 data.writeTo(buf);

dhfs-parent/server/src/main/resources/application.properties

@@ -13,7 +13,7 @@ dhfs.fuse.root=${HOME}/dhfs_default/fuse
 dhfs.fuse.debug=false
 dhfs.fuse.enabled=true
 dhfs.files.allow_recursive_delete=false
-dhfs.files.target_chunk_size=524288
+dhfs.files.target_chunk_size=2097152
 # Writes strictly smaller than this will try to merge with blocks nearby
 dhfs.files.write_merge_threshold=0.8
 # If a merge would result in a block of greater size than this, stop merging

dhfs-parent/server/src/test/java/com/usatiuk/dhfs/integration/DhfsFuseIT.java

@@ -45,6 +45,7 @@ public class DhfsFuseIT {
                                 .run("apt update && apt install -y libfuse2 curl")
                                 .copy("/app", "/app")
                                 .cmd("java", "-ea", "-Xmx128M", "--add-exports", "java.base/sun.nio.ch=ALL-UNNAMED",
+                                        "--add-exports", "java.base/jdk.internal.access=ALL-UNNAMED",
                                         "-Ddhfs.objects.peerdiscovery.interval=100",
                                         "-Ddhfs.objects.invalidation.delay=100",
                                         "-Ddhfs.objects.ref_verification=true",

dhfs-parent/server/src/test/java/com/usatiuk/dhfs/integration/DhfsFusex3IT.java

@@ -49,6 +49,7 @@ public class DhfsFusex3IT {
                                 .run("apt update && apt install -y libfuse2 curl gcc")
                                 .copy("/app", "/app")
                                 .cmd("java", "-ea", "-Xmx128M", "--add-exports", "java.base/sun.nio.ch=ALL-UNNAMED",
+                                        "--add-exports", "java.base/jdk.internal.access=ALL-UNNAMED",
                                         "-Ddhfs.objects.peerdiscovery.interval=100",
                                         "-Ddhfs.objects.invalidation.delay=100",
                                         "-Ddhfs.objects.deletion.delay=0",