On Wed, 5 Jun 2024 12:36:33 GMT, Jan Lahoda <[email protected]> wrote:
>> Consider these two programs:
>>
>>
>> public class SystemPrint {
>> public static void main(String... args) {
>> System.err.println("Hello!");
>> }
>> }
>>
>> and:
>>
>> public class IOPrint {
>> public static void main(String... args) {
>> java.io.IO.println("Hello!");
>> }
>> }
>>
>>
>> They do the same conceptual thing - write a text to the output. But,
>> `IO.println` delegates to `Console.println`, which then delegates to a
>> `Console` backend, and the default backend is currently based on JLine.
>>
>> The issues is that JLine takes a quite a long time to initialize, and in a
>> program like this, JLine is not really needed - it is used to provide better
>> editing experience when reading input, but there's no reading in these
>> programs.
>>
>> For example, on my computer:
>>
>> $ time java -classpath /tmp SystemPrint
>> Hello!
>>
>> real 0m0,035s
>> user 0m0,019s
>> sys 0m0,019s
>>
>> $ time java -classpath /tmp --enable-preview IOPrint
>> Hello!
>>
>> real 0m0,165s
>> user 0m0,324s
>> sys 0m0,042s
>>
>>
>> The proposal herein is to delegate to the simpler `Console` backend from
>> `java.base` as long as the user only uses methods that print to output, and
>> switch to the JLine delegate when other methods (typically input) is used.
>> Note that while technically `writer()` is a method doing output, it will
>> force JLine initialization to avoid possible problems if the client caches
>> the writer and uses it after switching the delegates.
>>
>> With this patch, I can get timing like this:
>>
>> $ time java --enable-preview -classpath /tmp/ IOPrint
>> Hello!
>>
>> real 0m0,051s
>> user 0m0,038s
>> sys 0m0,020s
>>
>>
>> which seems much more acceptable.
>>
>> There is also #19467, which may reduce the time further.
>>
>> A future work might focus on making JLine initialize faster, but avoiding
>> JLine initialization in case where we don't need it seems like a good step
>> to me in any case.
>
> Jan Lahoda has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Correctly reflecting review feedback
LGTM. Thanks for the changes.
-------------
Marked as reviewed by naoto (Reviewer).
PR Review: https://git.openjdk.org/jdk/pull/19479#pullrequestreview-2099801902
