Patch: Add methods to GCInfo to allow GC_free_space_divisor to be manipulated.

[David Daney <ddaney at avtrex dot com>]

Ever since the GC's internal symbols quit being exported by libgcj.so, 
it has been impossible to change the GC_free_space_divisor.  We need to 
be able to tune this value in restricted memory environments to prevent 
OutOfMemoryErrors.

This patch adds a couple of methods to the new gnu.gcj.util.GCInfo class 
that allow the GC_free_space_divisor parameter to be tuned.

Tested on x86_64-pc-linux-gnu.

OK to commit?

2007-10-18  David Daney  <ddaney@avtrex.com>

   * gnu/gcj/util/GCInfo.java (checkPermission): Renamed to ...
   (checkDumpPermission): ... this and updated references throughout.
   (checkParametersPermission, getGCFreeSpaceDivisor,
   setGCFreeSpaceDivisor): New methods.
   (getGCFreeSpaceDivisor0, setGCFreeSpaceDivisor0): Declare.
   * gnu/gcj/util/natGCInfo.cc: Move #includes outside of ifdef block.
   (getGCFreeSpaceDivisor0, setGCFreeSpaceDivisor0): New methods.
   * gnu/gcj/util/GCInfo.h: Regenerate.
   * classpath/lib/gnu/gcj/util/GCInfo.class: Ditto.

Index: gnu/gcj/util/GCInfo.java
===================================================================
--- gnu/gcj/util/GCInfo.java	(revision 129428)
+++ gnu/gcj/util/GCInfo.java	(working copy)
@@ -19,13 +19,60 @@ public class GCInfo
    * @throws SecurityException if there is a SecurityManager installed
    * and UtilPermission("dumpHeap") is not granted.
    */
-  private static void checkPermission()
+  private static void checkDumpPermission()
   {
     SecurityManager sm = System.getSecurityManager();
     if (sm != null)
       sm.checkPermission(new UtilPermission("dumpHeap"));
   }
-  
+
+  /**
+   * @throws SecurityException if there is a SecurityManager installed
+   * and UtilPermission("dumpHeap") is not granted.
+   */
+  private static void checkParametersPermission()
+  {
+    SecurityManager sm = System.getSecurityManager();
+    if (sm != null)
+      sm.checkPermission(new UtilPermission("changeGCParameters"));
+  }
+
+  /**
+   * Get the garbage collector's GC_free_space_divisor parameter.
+   *
+   * @return the divisor.
+   *
+   * @throws SecurityException if there is a SecurityManager installed
+   * and UtilPermission("changeGCParameters") is not granted.
+   */
+  public static int getGCFreeSpaceDivisor()
+  {
+    checkParametersPermission();
+    return getGCFreeSpaceDivisor0();
+  }
+
+  private static native int getGCFreeSpaceDivisor0();
+
+  /**
+   * Set the garbage collector's GC_free_space_divisor parameter.  The
+   * divisor may be set to a value greater than zero.
+   *
+   * @param divisor The new divisor value.
+   *
+   * @throws SecurityException if there is a SecurityManager installed
+   * and UtilPermission("changeGCParameters") is not granted.
+   *
+   * @throws IllegalArgumentException if divisor is not greater than zero.
+   */
+  public static void setGCFreeSpaceDivisor(int divisor)
+  {
+    checkParametersPermission();
+    if (divisor < 1)
+      throw new IllegalArgumentException();
+    setGCFreeSpaceDivisor0(divisor);
+  }
+
+  private static native void setGCFreeSpaceDivisor0(int divisor);
 
   /**
    * Dump a description of the heap state.
@@ -37,12 +84,11 @@ public class GCInfo
    */
   public static synchronized void dump(String name)
   {
-    checkPermission();
+    checkDumpPermission();
     dump0(name);
   }
-  
-  private static native void dump0(String name);
 
+  private static native void dump0(String name);
 
   /**
    * Create a heap dump.
@@ -54,10 +100,10 @@ public class GCInfo
    */
   public static synchronized void enumerate(String namePrefix)
   {
-    checkPermission();
+    checkDumpPermission();
     enumerate0(namePrefix);
   }
-  
+
   private static native void enumerate0(String namePrefix);
 
   /**
@@ -71,9 +117,9 @@ public class GCInfo
    */
   public static synchronized void setOOMDump(String namePrefix)
   {
-    checkPermission();
+    checkDumpPermission();
     setOOMDump0(namePrefix);
   }
-  
+
   private static native void setOOMDump0(String namePrefix);
 }

Index: gnu/gcj/util/natGCInfo.cc
===================================================================
--- gnu/gcj/util/natGCInfo.cc	(revision 129428)
+++ gnu/gcj/util/natGCInfo.cc	(working copy)
@@ -14,10 +14,6 @@
 
 #include <gnu/gcj/util/GCInfo.h>
 
-#ifdef HAVE_PROC_SELF_MAPS
-//
-// If /proc/self/maps does not exist we assume we are doomed and do nothing.
-//
 #include <stdio.h>
 #include <stdlib.h>
 #include <fcntl.h>
@@ -60,9 +56,10 @@ extern "C" {
   extern int GC_gcj_debug_kind;
 }
 
-#endif
-
 #ifdef HAVE_PROC_SELF_MAPS
+//
+// If /proc/self/maps does not exist we assume we are doomed and do nothing.
+//
 
 static int gc_ok = 1;
 
@@ -456,3 +453,14 @@ void
 
 #endif // HAVE_PROC_SELF_MAPS
 
+jint
+::gnu::gcj::util::GCInfo::getGCFreeSpaceDivisor0()
+{
+  return GC_free_space_divisor;
+}
+
+void
+::gnu::gcj::util::GCInfo::setGCFreeSpaceDivisor0(jint d)
+{
+  GC_free_space_divisor = d;
+}