8265612: revise the help info for jmap histo command

Reviewed-by: cjplummer, sspitsyn

Author: Lin Zang

src/jdk.jcmd/share/classes/sun/tools/jmap/JMap.java

@@ -226,11 +226,11 @@ private static void dump(String pid, String options)
             } else if (subopt.equals("format=b")) {
                 // ignore format (not needed at this time)
             } else if (subopt.startsWith("gz=")) {
-               compress_level = subopt.substring("gz=".length());
-               if (compress_level.length() == 0) {
+                compress_level = subopt.substring("gz=".length());
+                if (compress_level.length() == 0) {
                     System.err.println("Fail: no number provided in option: '" + subopt + "'");
                     usage(1);
-               }
+                }
             } else {
                 System.err.println("Fail: invalid option: '" + subopt + "'");
                 usage(1);
@@ -316,13 +316,13 @@ private static void usage(int exit) {
         System.err.println("    Example: jmap -dump:live,format=b,file=heap.bin <pid>");
         System.err.println("");
         System.err.println("    histo-options:");
-        System.err.println("      live         count only live objects (takes precedence if both \"live\" and \"all\" are specified)");
-        System.err.println("      all          count all objects in the heap (default if one of \"live\" or \"all\" is not specified)");
-        System.err.println("      file=<file>  dump data to <file>");
-        System.err.println("      parallel=<number>  parallel threads number for heap iteration:");
-        System.err.println("                                  parallel=0 default behavior, use predefined number of threads");
-        System.err.println("                                  parallel=1 disable parallel heap iteration");
-        System.err.println("                                  parallel=<N> use N threads for parallel heap iteration");
+        System.err.println("      live                count only live objects (takes precedence if both \"live\" and \"all\" are specified)");
+        System.err.println("      all                 count all objects in the heap (default if one of \"live\" or \"all\" is not specified)");
+        System.err.println("      file=<file>         dump data to <file>");
+        System.err.println("      parallel=<number>   Number of parallel threads to use for heap inspection:");
+        System.err.println("                          0 (the default) means let the VM determine the number of threads to use");
+        System.err.println("                          1 means use one thread (disable parallelism).");
+        System.err.println("                          For any other value the VM will try to use the specified number of threads, but might use fewer.");
         System.err.println("");
         System.err.println("    Example: jmap -histo:live,file=/tmp/histo.data <pid>");
         System.exit(exit);