RFR 4947890 : Minimize JNI upcalls in system-properties initialization

[Mandy Chung]

Hi Roger,

The system property initialization long for a clean up.
Thanks for looking at it.  This is a good start.  I think
it'd be good to make further improvement.

140 cmdProps = JVM_GetProperties(env); Instead of prepending the 
predefined set of properties with cmdProps, I suggest to separate 
getRawProperties into two separate methods 1. get the system properties 
defined by -D 2. the predefined properties

176 PUTPROP(propArray, _java_specification_version_NDX, 
VERSION_SPECIFICATION);
177 PUTPROP(propArray, _java_specification_name_NDX, "Java Platform API 
Specification");
178 PUTPROP(propArray, _java_specification_vendor_NDX, 
JAVA_SPECIFICATION_VENDOR);
179
180 PUTPROP(propArray, _java_vendor_NDX, VENDOR);
181 PUTPROP(propArray, _java_vendor_url_NDX, VENDOR_URL);
182 PUTPROP(propArray, _java_vendor_url_bug_NDX, VENDOR_URL_BUG);
183
184 jio_snprintf(buf, sizeof(buf), "%d.%d", JVM_CLASSFILE_MAJOR_VERSION,
185 JVM_CLASSFILE_MINOR_VERSION);
186 PUTPROP(propArray, _java_class_version_NDX, buf);

These are defined at build time.  Can they be moved to 
VersionProps.java.template?

130 // Get the platform specific values
  131     sprops = GetJavaProperties(env);
   :
  191     PUTPROP(propArray, _os_name_NDX, sprops->os_name);
  192     PUTPROP(propArray, _os_version_NDX, sprops->os_version);
  193     PUTPROP(propArray, _os_arch_NDX, sprops->os_arch);

This obtains the platform-specific configuration and then later
sets the value in the array of a predefined index.

Have you considered other alternatives?  SystemProps.Raw can
define the named prop value instead of index e.g.
    private static String _os_arch;

these fields are set via JNI.  Or have the native method
to return Object[] with the property name/value pair as
in the VM.

SystemProps.java

   69         putIfAbsent(props, "user.name", raw.propDefault(Raw._user_name_NDX));
   70         putIfAbsent(props, "os.name", raw.propDefault(Raw._os_name_NDX));
   71         putIfAbsent(props, "os.arch", raw.propDefault(Raw._os_arch_NDX));
   72         putIfAbsent(props, "os.version", raw.propDefault(Raw._os_version_NDX));
   73         putIfAbsent(props, "line.separator", raw.propDefault(Raw._line_separator_NDX));
   74         putIfAbsent(props, "file.separator", raw.propDefault(Raw._file_separator_NDX));
   75         putIfAbsent(props, "path.separator", raw.propDefault(Raw._path_separator_NDX));


jdk.internal.util.StaticProperty calls System.getProperty.
Should we move the above (or more) static properties and
initialize their values directly in StaticProperty class?
This is out of the scope of this issue but if we initialize
the field values directly via JNI.  Something that might
worth exploring.

thanks
Mandy