RFR: 8309390: [JVMCI] improve copying system properties into libgraal [v4]

[Doug Simon]

> This PR reduces the amount of code executed during libgraal initialization. This not only improves VM startup overall but all fixes a number of JDK test failures that are caused by Java code executing "too early". For example, `java/util/Locale/CompatWarning.java` can fail if `sun.util.locale.provider.LocaleProviderAdapter` is initialized before the `CheckWarning` handler is registered.
> 
> Instead of serializing `VM.savedProps` via `VMSupport.serializeSavedPropertiesToByteArray`, the `jdk.vm.ci.services.Services` class now directly reads `Arguments::system_properties()` using `Unsafe`. Furthermore, the value of a system property is lazily converted to a `String` from a C string pointer.
> 
> ## Times
> 
> The basic benchmarking below shows that this change brings the time for a nop Java app with eager libgraal initialization (2) down to almost the same time as lazy libgraal initialization (1). The latter typically means no libgraal initialization happens as a top tier JIT compilation is never scheduled in such a short running app.
> 
> 
> public class Nop {
>     public static void main(String[] args) {}
> }
> 
> 
> (1) Baseline (no options):
> 
>> for i in (seq 10); java Nop; end
>         0.05 real         0.04 user         0.01 sys
>         0.04 real         0.03 user         0.01 sys
>         0.04 real         0.03 user         0.01 sys
>         0.04 real         0.03 user         0.01 sys
>         0.03 real         0.03 user         0.00 sys
>         0.04 real         0.03 user         0.01 sys
>         0.04 real         0.03 user         0.00 sys
>         0.03 real         0.03 user         0.00 sys
>         0.04 real         0.03 user         0.01 sys
>         0.03 real         0.03 user         0.00 sys
> 
> 
> (2) Eagerly initialize libgraal (with PR):
> 
>> for i in (seq 10); /usr/bin/time java -XX:+EagerJVMCI Nop; end
>         0.06 real         0.04 user         0.01 sys
>         0.05 real         0.03 user         0.01 sys
>         0.05 real         0.03 user         0.01 sys
>         0.05 real         0.03 user         0.01 sys
>         0.05 real         0.03 user         0.01 sys
>         0.05 real         0.03 user         0.01 sys
>         0.05 real         0.03 user         0.01 sys
>         0.05 real         0.03 user         0.01 sys
>         0.05 real         0.03 user         0.01 sys
>         0.05 real         0.03 user         0.01 sys
> 
> 
> (3) Eagerly initialize libgraal (without PR):
> 
>> for i in (seq 10); /usr/bin/time java -XX:+EagerJVMCI Nop; end
>         0.11 real         0.08 user         ...

Doug Simon has updated the pull request incrementally with one additional commit since the last revision:

  reduced complexity of SystemProperties based on it being unmodifiable

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14291/files
  - new: https://git.openjdk.org/jdk/pull/14291/files/7a82c24e..6c346d35

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14291&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14291&range=02-03

  Stats: 207 lines in 2 files changed: 33 ins; 160 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/14291.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14291/head:pull/14291

PR: https://git.openjdk.org/jdk/pull/14291