RFR: 8355638: Allow -Xlog:aot to be used as an alias for -Xlog:cds when using AOT cache [v6]

[Stefan Karlsson]

On Thu, 8 May 2025 02:59:35 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> *Specification:*
>> 
>> When the JVM is started with any of the following options: AOTCache, AOTCacheOutput, AOTConfiguration, AOTMode:
>> 
>> - Any `-Xlog` options that starts with the `aot` tag should also match any `LogTagSets` whose first tag is `LogTag::_cds`
>> - When printing a `LogTagSet` whose first tag is `LogTag::_cds`, if its `tags` decoration is to be printed, then the first tag in the decoration should be printed as `aot`.
>> 
>> *Examples:*
>> 
>> Control case -- this is an example of an old "cds" log. The decoration should be printed as "cds" to be backwards compatible
>> 
>> $ java -Xshare:auto -Xlog:cds --version | grep trying
>> [0.003s][info][cds] trying to map /jdk3/bld/vox/images/jdk/lib/server/classes.jsa
>> 
>> 
>> "aot" can be used to select the "cds" log, but the log will be printed with "aot" as its decoration
>> 
>> $ java -XX:AOTMode=auto -Xlog:aot --version | grep trying
>> [0.015s][info][aot] trying to map /jdk3/bld/vox/images/jdk/lib/server/classes.jsa
>> 
>> 
>> When using new -XX:AOT flags, even if you specify -Xlog:cds, the output will use "aot" decoration
>> 
>> $ java -XX:AOTMode=auto -Xlog:cds --version | grep tryi
>> [0.004s][info][aot] trying to map /jdk3/bld/vox/images/jdk/lib/server/classes.jsa
>> 
>> 
>> When using new -XX:AOT flags, error messages should be logged with "aot" decoration even when no -Xlog flags are specified
>> 
>> $ java -XX:AOTMode=auto -XX:AOTCache=nofile.aot --version
>> [0.009s][error][aot] An error has occurred while processing the AOT cache. Run with -Xlog:aot for details.
>> [0.009s][error][aot] Loading AOT cache failed: nofile.aot
>> java 25-internal 2025-09-16
>> Java(TM) SE Runtime Environment (build 25-internal-adhoc.iklam.vox)
>> Java HotSpot(TM) 64-Bit Server VM (build 25-internal-adhoc.iklam.vox, mixed mode)
>
> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Removed checks for error message that got removed from the PR

This seems like a hack in the UL system. Did you consider confining this in the CDS / AOT code instead? 

Something like this pseudo code:

bool aot_log_is_enabled(Level, ...) {
  return log_is_enabled(Level, aot, link) ||
         log_is_enabled(Level, cds, link);
}
void aot_log_info(...) {}
...
if (aot_log_is_enabled(Info, link) {
  ResourceMark rm;
  aot_log_info(link)("%s %s %p", class_category_name(ik), ik->external_name(), ik);
}

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

PR Comment: https://git.openjdk.org/jdk/pull/24895#issuecomment-2863605568