RFR: 8355798: Implement JEP 514: Ahead-of-Time Command Line Ergonomics [v8]

[Ioi Lam]

On Wed, 14 May 2025 15:38:06 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Ioi Lam has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - java.md updates from @rose00
>>  - Resolved differences with CSR JDK-8356010
>
> src/hotspot/share/cds/cds_globals.hpp line 123:
> 
>> 121:   product(ccstr, AOTCacheOutput, nullptr,                                   \
>> 122:           "Write AOT cache into this file (overrides AOTCache when "        \
>> 123:           "writing)")                                                       \
> 
> This looks not complete description. And "override AOTCache .." is confusing.

I changed it to "Specifies the file name for writing the AOT cache". Since the behavior is complex, I don't know how much detail I should put here.

> src/hotspot/share/cds/metaspaceShared.cpp line 1150:
> 
>> 1148:   print_java_launcher(&ss);
>> 1149:   const char* cmd = ss.freeze();
>> 1150:   tty->print_cr("Launching child process %s to assemble AOT cache %s using configuration %s", cmd, AOTCacheOutput, AOTConfiguration);
> 
> I noticed that AOT produces outputs on TTY like this unconditionally. I think it is fine for development but for production we should use UL I think.
> Was this discussed?

Currently we print things that are important to the user. The other examples are:


$ java -XX:AOTMode=record ....
AOTConfiguration recorded: hw.aotconfig

$ java -XX:AOTMode=create ....
Reading AOTConfiguration hw.aotconfig and writing AOTCache hw.aot
AOTCache creation is complete: hw.aot 10498048 bytes


I think AOT is still a new feature so a small number of TTY prints would be helpful. If people complain about the verbosity we can change them to UL logs.

> src/hotspot/share/runtime/arguments.cpp line 3060:
> 
>> 3058: }
>> 3059: 
>> 3060: static JavaVMOption* get_last_aotmode_arg(const JavaVMInitArgs* args) {
> 
> I don't like that we pollute `Arguments` code with AOT specific flags processing.
> Can we move this into `CDSConfig`? Both these 2 new methods.
> 
> But I will agree if you want to keep it here. It is not critical.

These two functions are for parsing `JDK_AOT_VM_OPTIONS`, so I think they belong to arguments.cpp. cdsConfig.cpp is a consumer of the options parsed by arguments.cpp.

> src/java.base/share/man/java.md line 4141:
> 
>> 4139:        mode should be used only as a "fail-fast" debugging aid to check if your command-line
>> 4140:        options are compatible with the AOT cache. An alternative is to run your application with
>> 4141:        `-XX:AOTMode=auto -Xlog:cds,aot` to see if the AOT cache can be used or not.
> 
> `-Xlog:aot`

`-Xlog:cds,aot` is correct for the current state of this PR. I'll change it after JDK-8356595 is integrated into the mainline.

> test/hotspot/jtreg/runtime/cds/appcds/aotFlags/AOTFlags.java line 166:
> 
>> 164:             "-XX:-AOTClassLinking",
>> 165:             "-XX:AOTConfiguration=" + aotConfigFile,
>> 166:             "-Xlog:cds=debug",
> 
> `-Xlog:aot`
> I assume JDK-8356595: "Convert -Xlog:cds to -Xlog:aot " will be pushed first.

`-Xlog:cds=debug` is correct for the current state of this PR (otherwise the test will fail). I'll change it after JDK-8356595 is integrated into the mainline.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24942#discussion_r2090133925
PR Review Comment: https://git.openjdk.org/jdk/pull/24942#discussion_r2090133649
PR Review Comment: https://git.openjdk.org/jdk/pull/24942#discussion_r2090133612
PR Review Comment: https://git.openjdk.org/jdk/pull/24942#discussion_r2090133585
PR Review Comment: https://git.openjdk.org/jdk/pull/24942#discussion_r2090133557