RFR: 8309390: [JVMCI] improve copying system properties into libgraal [v3]

[Tom Rodriguez]

On Mon, 12 Jun 2023 09:20:09 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> src/jdk.internal.vm.ci/share/classes/jdk/vm/ci/services/Services.java line 314:
>> 
>>> 312:             String key = toJavaString(unsafe, unsafe.getLong(prop + keyOffset));
>>> 313:             long valueAddress = unsafe.getLong(prop + valueOffset);
>>> 314:             if (valueAddress != 0) {
>> 
>> Is the lazy value construction really necessary?  It seems like it requires quite a bit of extra machinery.
>
> In big apps, I image there can be quite some large system property values (e.g. `java.class.path`) so we don't want to pay memory overhead per libgraal isolate for such properties as they're ignored by libgraal.
> 
> I realized I can reduce the extra machinery based on the fact that `SystemProperties` is unmodifiable: https://github.com/openjdk/jdk/pull/14291/commits/6c346d35923402fb5d6ae0ef83214f8f0ca07b69
> The only method that still eager converts the string is `SystemProperties.values()` but that's fine as it's not used by JVMCI or Graal.
> I think the trade off is now acceptable?

Yes I like this trade off a bit better.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/14291#discussion_r1226857200