On Tue, 29 Apr 2025 15:29:08 GMT, Vladimir Kozlov <k...@openjdk.org> wrote:
>> [JEP 483](https://bugs.openjdk.org/browse/JDK-8315737) preserves class >> information in AOT cache which helps Java startup performance. >> >> We should also preserve adapters (i2c, c2i) to further improve performance >> of class linking where adapters are generated. >> >> Short running Java application can see several percents improvement. I got >> 6% improvement when ran `HelloWorld.java` on Linux-x64 Ice Lake CPU (2.5Ghz): >> >> >> (perf stat -r 100 java -XX:AOTCache=app.aotcache -cp hello.jar HelloWorld > >> /dev/null) 2>&1 | grep elapsed >> 0.0299401 +- 0.0000504 seconds time elapsed ( +- 0.17% ) >> >> (perf stat -r 100 java -XX:AOTCache=app.aotcache >> -XX:+UnlockDiagnosticVMOptions -XX:-AOTAdapterCaching -cp hello.jar >> HelloWorld > /dev/null) 2>&1 | grep elapsed >> 0.0318654 +- 0.0000535 seconds time elapsed ( +- 0.17% ) >> >> >> New diagnostic flags are introduced (use `-XX:+UnlockDiagnosticVMOptions` to >> unlock them): >> >> >> -XX:+AOTAdapterCaching - Enable or disable saving and restoring i2c2i >> adapters >> -XX:AOTCodeMaxSize=10*M - buffer size in bytes for AOT code caching >> -XX:+AbortVMOnAOTCodeFailure - Abort VM on the first occurrence of AOT code >> caching failure >> >> By default `AOTAdapterCaching` is `false` and enabled ergonomically when >> `-XX:AOTCache` is specified. >> This flag is ignored when `AOTCache` is not specified. >> >> To use AOT adapters follow process described in JEP 483: >> >> >> java -XX:AOTMode=record -XX:AOTConfiguration=app.aotconf -cp app.jar App >> java -XX:AOTMode=create -XX:AOTConfiguration=app.aotconf >> -XX:AOTCache=app.aot -cp app.jar >> java -XX:AOTCache=app.aot -cp app.jar App >> >> >> There are several new UL flag combinations to trace the AOT code caching >> process: >> >> >> -Xlog:aot+codecache+init -Xlog:aot+codecache+exit -Xlog:aot+codecache+stubs >> >> >> @ashu-mehra is main author of changes. He implemented adapters caching. >> I did main framework (`AOTCodeCache` class) for saving and loading AOT code. >> >> Tested tier1-6,10, which includes tests with `AOTClassLinking` enabled. Also >> Xcomp,stress and JCK. > > Vladimir Kozlov has updated the pull request incrementally with one > additional commit since the last revision: > > Remove unused method LGTM. Some small nits. src/hotspot/share/cds/filemap.cpp line 1296: > 1294: mapped_base = requested_base; > 1295: } else { > 1296: bool read_only = false, allow_exec = false; Add comment for clarity: // We do not execute in-place in the AOT code region. AOT code is copied to // the CodeCache for execution. bool read_only = false, allow_exec = false; src/hotspot/share/include/cds.h line 38: > 36: // Also, this is a C header file. Do not use C++ here. > 37: > 38: #define NUM_CDS_REGIONS 5 // this must be the same as > MetaspaceShared::n_regions Change `CURRENT_CDS_ARCHIVE_VERSION` below to `19` ------------- Marked as reviewed by iklam (Reviewer). PR Review: https://git.openjdk.org/jdk/pull/24740#pullrequestreview-2805483199 PR Review Comment: https://git.openjdk.org/jdk/pull/24740#discussion_r2067701064 PR Review Comment: https://git.openjdk.org/jdk/pull/24740#discussion_r2067702057
