8286677: [BACKOUT] (fc) Tune FileChannel.transferFrom()

Reviewed-by: dholmes, mikael

Author: Brian Burkhalter

src/java.base/share/classes/sun/nio/ch/FileChannelImpl.java

@@ -541,9 +541,9 @@ public void force(boolean metaData) throws IOException {
     }
 
     // Assume at first that the underlying kernel supports sendfile();
-    // set this to true if we find out later that it doesn't
+    // set this to false if we find out later that it doesn't
     //
-    private static volatile boolean transferToNotSupported;
+    private static volatile boolean transferSupported = true;
 
     // Assume that the underlying kernel sendfile() will work if the target
     // fd is a pipe; set this to false if we find out later that it doesn't
@@ -587,7 +587,7 @@ private long transferToDirectlyInternal(long position, int icount,
             }
             if (n == IOStatus.UNSUPPORTED) {
                 // Don't bother trying again
-                transferToNotSupported = true;
+                transferSupported = false;
                 return IOStatus.UNSUPPORTED;
             }
             return IOStatus.normalize(n);
@@ -601,7 +601,7 @@ private long transferToDirectly(long position, int icount,
                                     WritableByteChannel target)
         throws IOException
     {
-        if (transferToNotSupported)
+        if (!transferSupported)
             return IOStatus.UNSUPPORTED;
 
         FileDescriptor targetFD = null;
@@ -646,9 +646,8 @@ private long transferToDirectly(long position, int icount,
     }
 
     // Size threshold above which to use a mapped buffer;
-    // transferToArbitraryChannel() and transferFromArbitraryChannel()
-    // are faster for smaller transfers
-    private static final long MAPPED_TRANSFER_THRESHOLD = 16L*1024L;
+    // transferToArbitraryChannel() is faster for smaller transfers
+    private static final long TRUSTED_TRANSFER_THRESHOLD = 16L*1024L;
 
     // Maximum size to map when using a mapped buffer
     private static final long MAPPED_TRANSFER_SIZE = 8L*1024L*1024L;
@@ -657,7 +656,7 @@ private long transferToTrustedChannel(long position, long count,
                                           WritableByteChannel target)
         throws IOException
     {
-        if (count < MAPPED_TRANSFER_THRESHOLD)
+        if (count < TRUSTED_TRANSFER_THRESHOLD)
             return IOStatus.UNSUPPORTED_CASE;
 
         boolean isSelChImpl = (target instanceof SelChImpl);
@@ -782,66 +781,12 @@ public long transferTo(long position, long count,
         return transferToArbitraryChannel(position, count, target);
     }
 
-    // Assume at first that the underlying kernel supports copy_file_range();
-    // set this to true if we find out later that it doesn't
-    //
-    private static volatile boolean transferFromNotSupported;
-
-    private long transferFromDirectlyInternal(FileDescriptor srcFD,
-                                              long position, long count)
-        throws IOException
-    {
-        long n = -1;
-        int ti = -1;
-        try {
-            beginBlocking();
-            ti = threads.add();
-            if (!isOpen())
-                return -1;
-            do {
-                long comp = Blocker.begin();
-                try {
-                    n = transferFrom0(srcFD, fd, position, count);
-                } finally {
-                    Blocker.end(comp);
-                }
-            } while ((n == IOStatus.INTERRUPTED) && isOpen());
-            if (n == IOStatus.UNSUPPORTED) {
-                // Don't bother trying again
-                transferFromNotSupported = true;
-                return IOStatus.UNSUPPORTED;
-            }
-            return IOStatus.normalize(n);
-        } finally {
-            threads.remove(ti);
-            end (n > -1);
-        }
-    }
-
-    private long transferFromDirectly(FileChannelImpl src,
-                                      long position, long count)
-        throws IOException
-    {
-        if (!src.readable)
-            throw new NonReadableChannelException();
-        if (transferFromNotSupported)
-            return IOStatus.UNSUPPORTED;
-        FileDescriptor srcFD = src.fd;
-        if (srcFD == null)
-            return IOStatus.UNSUPPORTED_CASE;
-
-        return transferFromDirectlyInternal(srcFD, position, count);
-    }
-
     private long transferFromFileChannel(FileChannelImpl src,
                                          long position, long count)
         throws IOException
     {
         if (!src.readable)
             throw new NonReadableChannelException();
-        if (count < MAPPED_TRANSFER_THRESHOLD)
-            return IOStatus.UNSUPPORTED_CASE;
-
         synchronized (src.positionLock) {
             long pos = src.position();
             long max = Math.min(count, src.size() - pos);
@@ -931,10 +876,8 @@ public long transferFrom(ReadableByteChannel src,
             return 0;
 
         if (src instanceof FileChannelImpl fci) {
-            long n;
-            if ((n = transferFromDirectly(fci, position, count)) >= 0)
-                return n;
-            if ((n = transferFromFileChannel(fci, position, count)) >= 0)
+            long n = transferFromFileChannel(fci, position, count);
+            if (n >= 0)
                 return n;
         }
 
@@ -1568,10 +1511,6 @@ private native long map0(int prot, long position, long length, boolean isSync)
     private static native long transferTo0(FileDescriptor src, long position,
                                            long count, FileDescriptor dst);
 
-    private static native long transferFrom0(FileDescriptor src,
-                                             FileDescriptor dst,
-                                             long position, long count);
-
     // Retrieves the maximum size of a transfer
     private static native int maxDirectTransferSize0();
 

src/java.base/unix/native/libnio/ch/FileChannelImpl.c

@@ -31,7 +31,6 @@
 
 #if defined(__linux__)
 #include <sys/sendfile.h>
-#include <dlfcn.h>
 #elif defined(_AIX)
 #include <string.h>
 #include <sys/socket.h>
@@ -53,21 +52,11 @@
 
 static jfieldID chan_fd;        /* jobject 'fd' in sun.nio.ch.FileChannelImpl */
 
-#if defined(__linux__)
-typedef ssize_t copy_file_range_func(int, loff_t*, int, loff_t*, size_t,
-                                     unsigned int);
-static copy_file_range_func* my_copy_file_range_func = NULL;
-#endif
-
 JNIEXPORT jlong JNICALL
 Java_sun_nio_ch_FileChannelImpl_initIDs(JNIEnv *env, jclass clazz)
 {
     jlong pageSize = sysconf(_SC_PAGESIZE);
     chan_fd = (*env)->GetFieldID(env, clazz, "fd", "Ljava/io/FileDescriptor;");
-#if defined(__linux__)
-    my_copy_file_range_func =
-        (copy_file_range_func*) dlsym(RTLD_DEFAULT, "copy_file_range");
-#endif
     return pageSize;
 }
 
@@ -263,38 +252,6 @@ Java_sun_nio_ch_FileChannelImpl_transferTo0(JNIEnv *env, jobject this,
 #endif
 }
 
-JNIEXPORT jlong JNICALL
-Java_sun_nio_ch_FileChannelImpl_transferFrom0(JNIEnv *env, jobject this,
-                                              jobject srcFDO, jobject dstFDO,
-                                              jlong position, jlong count)
-{
-#if defined(__linux__)
-    if (my_copy_file_range_func == NULL)
-        return IOS_UNSUPPORTED;
-
-    jint srcFD = fdval(env, srcFDO);
-    jint dstFD = fdval(env, dstFDO);
-
-    off64_t offset = (off64_t)position;
-    jlong n = my_copy_file_range_func(srcFD, NULL, dstFD, &offset, count, 0);
-    if (n < 0) {
-        if (errno == EAGAIN)
-            return IOS_UNAVAILABLE;
-        if ((errno == EINVAL || errno == EXDEV) && ((ssize_t)count >= 0))
-            return IOS_UNSUPPORTED_CASE;
-        if (errno == EINTR) {
-            return IOS_INTERRUPTED;
-        }
-        JNU_ThrowIOExceptionWithLastError(env, "Transfer failed");
-        return IOS_THROWN;
-    }
-    return n;
-#else
-    return IOS_UNSUPPORTED;
-#endif
-}
-
-
 JNIEXPORT jint JNICALL
 Java_sun_nio_ch_FileChannelImpl_maxDirectTransferSize0(JNIEnv* env, jobject this)
 {

src/java.base/windows/native/libnio/ch/FileChannelImpl.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -193,13 +193,6 @@ Java_sun_nio_ch_FileChannelImpl_transferTo0(JNIEnv *env, jobject this,
     return chunkSize;
 }
 
-JNIEXPORT jlong JNICALL
-Java_sun_nio_ch_FileChannelImpl_transferFrom0(JNIEnv *env, jobject this,
-                                              jobject srcFDO, jobject dstFDO,
-                                              jlong position, jlong count)
-{
-    return IOS_UNSUPPORTED;
-}
 
 JNIEXPORT jint JNICALL
 Java_sun_nio_ch_FileChannelImpl_maxDirectTransferSize0(JNIEnv* env, jobject this)

test/jdk/java/nio/channels/FileChannel/Transfers.java

@@ -23,7 +23,7 @@
 
 /* @test
  * @summary Comprehensive test for FileChannel.transfer{From,To}
- * @bug 4708120 8274113
+ * @bug 4708120
  * @author Mark Reinhold
  * @run main/timeout=300 Transfers
  */
@@ -468,16 +468,10 @@ static void testFrom(long seed, Source src, FileChannel fc, int off, int len)
         int pos = (int)seed & 0xfff;
         fc.position(pos);
 
-        long position = off;
-        long count = len;
-        while (count > 0) {
-            int n = (int)fc.transferFrom(src.channel(), position, count);
-            if (n < 0 || n > count)
-                throw new Failure("Incorrect transfer length n = : " + n
-                                  + " (expected 0 <= n <= " + len + ")");
-            position += n;
-            count -= n;
-        }
+        int n = (int)fc.transferFrom(src.channel(), off, len);
+        if (n != len)
+            throw new Failure("Incorrect transfer length: " + n
+                              + " (expected " + len + ")");
 
         // Check that source didn't change, and was read correctly
         src.verify();