On Wed, 7 Jun 2023 22:51:48 GMT, Doug Simon <dnsi...@openjdk.org> wrote:
>> This PR improves the startup time for libgraal by speeding up how
>> `VM.savedProps` is copied into libgraal. This data structure is now
>> serialized to a native buffer directly from C++ and the native buffer is
>> then directly decoded by libgraal.
>>
>> ## 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 0.02 sys
>> 0.08 real 0.06 user 0.01 sys
>> 0.08 real 0.07 user 0.01 sys
>> 0.10 real 0.07 user 0.01 sys
>> 0.08 real 0.06 user 0.01 sys
>> 0.10 real 0.07 user 0.01 sys
>> 0.08 real 0.07 user 0.01 sys
>> 0.08 real ...
>
> Doug Simon has updated the pull request with a new target base due to a merge
> or a rebase. The pull request now contains two commits:
>
> - [skip ci] snapshot Arguments::system_properties() in JVMCI instead of
> System.savedProps
> - more efficient copying of system properties into libjvmci
src/hotspot/share/jvmci/jvmciJavaClasses.hpp line 60:
> 58: jvmci_constructor) \
> 59: start_class(Services, jdk_vm_ci_services_Services)
> \
> 60: jvmci_method(CallStaticVoidMethod, GetStaticMethodID, call_static,
> void, Services, initializeSavedProperties, byte_array_void_signature,
> (JVMCIObject serializedProperties)) \
The final arg for the `jvmci_method` macro is never used so I removed it
everywhere.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/14291#discussion_r1222257086
