Re: performance problems with classpath 0.09 on Jikes RVM

[David P Grove]

Here's a patch.  Works with Jikes
RVM and reduces our classpath 0.09 performance degradation on _228_jack
to a slightly more tolerable 5%.  Eliot's point is probably a good
one though, this is an unfortunate place to be having to cross JNI boundaries.
 Probably the right long term solution for Jikes RVM is to provide
our own all Java  version of FileChannelImpl that avoids exposing
us to the remaining performance problems.  This would also let us
hook into the nonblocking I/O layer in Jikes RVM if we wanted to. 

--dave

Index: gnu_java_nio_channels_FileChannelImpl.c
===================================================================
RCS file: /cvsroot/classpath/classpath/native/jni/java-nio/gnu_java_nio_channels_FileChannelImpl.c,v
retrieving revision 1.10
diff -u -r1.10 gnu_java_nio_channels_FileChannelImpl.c
--- gnu_java_nio_channels_FileChannelImpl.c        1 May 2004 10:40:56 -0000        1.10
+++ gnu_java_nio_channels_FileChannelImpl.c        8 May 2004 02:01:20 -0000
@@ -87,11 +87,27 @@
#define CONVERT_SSIZE_T_TO_JINT(x) ((jint)(x & 0xFFFFFFFF))
#define CONVERT_JINT_TO_SSIZE_T(x) (x)

+/* cache fieldID of gnu.java.nio.channels.FileChannelImpl.fd */
+static jfieldID native_fd_fieldID;
+
static jint get_native_fd(JNIEnv *env, jobject obj)
{
+  return (*env)->GetIntField (env, obj, native_fd_fieldID);
+}
+
+/*
+ * Library initialization routine.  Called as part of java.io.FileDescriptor
+ * static initialization.
+ */
+JNIEXPORT void JNICALL
+Java_gnu_java_nio_channels_FileChannelImpl_init (JNIEnv *env, jclass clazz)
+{
  jclass clazz_fc;
-  jfieldID field_fd;
+  jfieldID field;
+  jmethodID constructor;
+  jobject obj;

+  /* Initialize native_fd_fieldID so we only compute it once! */
  clazz_fc = (*env)->FindClass (env, "gnu/java/nio/channels/FileChannelImpl");
  if (!clazz_fc)
    {
@@ -99,26 +115,14 @@
      return -1;
    }

-  field_fd = (*env)->GetFieldID (env, clazz_fc, "fd", "I");
-  if (!field_fd)                                                        
+  field = (*env)->GetFieldID (env, clazz_fc, "fd", "I");
+  if (!field)                                                        
    {                                                                        
      JCL_ThrowException(env, IO_EXCEPTION, "Internal error");                
      return -1;                                                        
-    }                                                                        
-
-  return (*env)->GetIntField (env, obj, field_fd);
-}
+    }

-/*
- * Library initialization routine.  Called as part of java.io.FileDescriptor
- * static initialization.
- */
-JNIEXPORT void JNICALL
-Java_gnu_java_nio_channels_FileChannelImpl_init (JNIEnv *env, jclass clazz)
-{
-  jfieldID field;
-  jmethodID constructor;
-  jobject obj;
+  native_fd_fieldID = field;

  constructor = (*env)->GetMethodID (env, clazz, "<init>", "(II)V");
   if (! constructor)