On Sat, 21 Aug 2021 22:37:05 GMT, Mandy Chung <mch...@openjdk.org> wrote:
>> This reimplements core reflection with method handles. >> >> For `Constructor::newInstance` and `Method::invoke`, the new implementation >> uses `MethodHandle`. For `Field` accessor, the new implementation uses >> `VarHandle`. For the first few invocations of one of these reflective >> methods on a specific reflective object we invoke the corresponding method >> handle directly. After that we spin a dynamic bytecode stub defined in a >> hidden class which loads the target `MethodHandle` or `VarHandle` from its >> class data as a dynamically computed constant. Loading the method handle >> from a constant allows JIT to inline the method-handle invocation in order >> to achieve good performance. >> >> The VM's native reflection methods are needed during early startup, before >> the method-handle mechanism is initialized. That happens soon after >> System::initPhase1 and before System::initPhase2, after which we switch to >> using method handles exclusively. >> >> The core reflection and method handle implementation are updated to handle >> chained caller-sensitive method calls [1] properly. A caller-sensitive >> method can define with a caller-sensitive adapter method that will take an >> additional caller class parameter and the adapter method will be annotated >> with `@CallerSensitiveAdapter` for better auditing. See the detailed >> description from [2]. >> >> Ran tier1-tier8 tests. >> >> [1] https://bugs.openjdk.java.net/browse/JDK-8013527 >> [2] >> https://bugs.openjdk.java.net/browse/JDK-8271820?focusedCommentId=14439430&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14439430 > > Mandy Chung has updated the pull request incrementally with one additional > commit since the last revision: > > Remove separate accessor for static vs instance method > > There is no effective difference when using MethodHandle::dropArgument for > static method. Removing Static*Accessor and Instance*Accessor simplifies > the implementation. [cff856f](https://github.com/openjdk/jdk/pull/5027/commits/cff856f9df89293cbc8f2f1e977148cd6ece4f85) removed the distinct classes to specialize for static vs instance methods simplify the `DirectMethodAccessorImpl` implementation and its subclasses. There is no effective difference for static method invocation to drop the first argument via MethodHandle::dropArgument or special case it in `StaticMethodAccessor::invoke`. The cold startup time increases 4ms from 92.73ms to 96.80ms when MethodHandle::dropArgument is used. Current implementation Benchmark Mode Cnt Score Error Units ReflectionMethods.instance_method avgt 10 14.902 ? 0.031 ns/op ReflectionMethods.instance_method_3arg avgt 10 18.099 ? 0.632 ns/op ReflectionMethods.instance_method_var avgt 10 14.670 ? 0.044 ns/op ReflectionMethods.instance_method_var_3arg avgt 10 18.038 ? 0.109 ns/op ReflectionMethods.static_method avgt 10 20.140 ? 0.032 ns/op ReflectionMethods.static_method_3arg avgt 10 26.999 ? 0.046 ns/op ReflectionMethods.static_method_var avgt 10 22.272 ? 0.153 ns/op ReflectionMethods.static_method_var_3arg avgt 10 26.567 ? 0.088 ns/op No special casing for static vs instance methods Benchmark Mode Cnt Score Error Units ReflectionMethods.instance_method avgt 10 15.177 ? 0.032 ns/op ReflectionMethods.instance_method_3arg avgt 10 17.906 ? 0.050 ns/op ReflectionMethods.instance_method_var avgt 10 14.759 ? 0.083 ns/op ReflectionMethods.instance_method_var_3arg avgt 10 18.054 ? 0.197 ns/op ReflectionMethods.static_method avgt 10 13.599 ? 0.029 ns/op ReflectionMethods.static_method_3arg avgt 10 16.910 ? 0.099 ns/op ReflectionMethods.static_method_var avgt 10 13.993 ? 0.189 ns/op ReflectionMethods.static_method_var_3arg avgt 10 17.555 ? 0.068 ns/op $ perf stat -r 50 jep-build/linux-x86_64-server-release/images/jdk/bin/java -cp $MICRO_JAR org.openjdk.bench.java.lang.reflect.ReflectionColdstartBenchmark Performance counter stats for 'build/linux-x86_64-server-release/images/jdk/bin/java -cp build/linux-x86_64-server-release/images/test/micro/benchmarks.jar org.openjdk.bench.java.lang.reflect.ReflectionColdstartBenchmark' (50 runs): 138.361238 task-clock:u (msec) # 1.492 CPUs utilized ( +- 0.79% ) 0 context-switches:u # 0.000 K/sec 0 cpu-migrations:u # 0.000 K/sec 4029 page-faults:u # 0.029 M/sec ( +- 0.12% ) 165249965 cycles:u # 1.194 GHz ( +- 0.85% ) 187374236 instructions:u # 1.13 insn per cycle ( +- 0.44% ) 35240188 branches:u # 254.697 M/sec ( +- 0.46% ) 1205192 branch-misses:u # 3.42% of all branches ( +- 1.15% ) 0.092733825 seconds time elapsed ( +- 1.02% ) $ perf stat -r 50 build/linux-x86_64-server-release/images/jdk/bin/java -cp $MICRO_JAR org.openjdk.bench.java.lang.reflect.ReflectionColdstartBenchmark Performance counter stats for 'build/linux-x86_64-server-release/images/jdk/bin/java -cp build/linux-x86_64-server-release/images/test/micro/benchmarks.jar org.openjdk.bench.java.lang.reflect.ReflectionColdstartBenchmark' (50 runs): 153.339577 task-clock:u (msec) # 1.584 CPUs utilized ( +- 0.83% ) 0 context-switches:u # 0.000 K/sec 0 cpu-migrations:u # 0.000 K/sec 4129 page-faults:u # 0.027 M/sec ( +- 0.10% ) 187019454 cycles:u # 1.220 GHz ( +- 1.06% ) 203065287 instructions:u # 1.09 insn per cycle ( +- 0.34% ) 38350445 branches:u # 250.101 M/sec ( +- 0.36% ) 1385764 branch-misses:u # 3.61% of all branches ( +- 1.08% ) 0.096803078 seconds time elapsed ( +- 1.07% ) Note that static_method* are slower than instance_method* in the current implementation but seem to perform better after this patch. Claes looked into the current implementation via the disassembly and found that instance_method* get a more optimal code shape at the call-site but static_methods* do not. With this patch, we will need to look closer if instance_method* and static_method* benchmarks probbly get the optimal code shape at the call-site. ------------- PR: https://git.openjdk.java.net/jdk/pull/5027
