Passing ziptime-info=false to ZipFileSystemProvider (along with other classpath performance ideas)

[Jaikiran Pai]

Hello Jason,

On 02/03/25 7:13 pm, Jason Zaugg wrote:
> I've been analysing the performance of javac in a relatively large 
> codebase and found classpath scanning to be the dominant factor. There 
> are large numbers of compilation tasks, most with long classpaths 
> including large JARs.
>
> I've been using the wall-time profiling mode of async-profiler to 
> analyse where time is being spent.
>
> I've been able improve build times (most dramatically on Windows, 750s 
> reduced to 350s) by modifying javac to:
>
> 1. pass ziptime-info=false to the env Map of 
> jarFsProvider.newFileSystem, which means the classpath scan in the 
> constructor of ArchiveContainer need only read the ZIP central 
> directory, rather then reading per-entry Extended Time metadata.

I am not familiar with the compiler implementation code, but speaking in 
context of the ZipFileSystem, it appears that this (undocumented) 
"ziptime-info" property of the ZIP file system was indeed introduced to 
help improve the performance of the ZipFileSystem. Setting it to false 
implies that the lastAccessTime() and the creationTime() returned by the 
ZipFileAttributes may not be accurate for some entries, since settings 
this property to false skips reading the per entry creation and access 
time information for the entries. Would you happen to know if either of 
these two methods are used in the code path where you are proposing to 
add "ziptime-info=false"?

-Jaikiran