haglin

قبل 19 يومًاdiscuss

I work on OpenJDK, so I may be biased, but I’ve also found that JFR works really well with LLMs.

  $ java -XX:StartFlightRecording:maxsize=10M,filename=dump.jfr -jar app.jar

  $ jfr view all-views dump.jfr > report.txt

  $ jfr print dump.jfr > all.txt

Then ask Codex, or whatever AI tool you use, to analyze report.txt for issues and use all.txt to dig deeper, if needed.

haglin

قبل 9 أشهرdiscuss

I find inheritance works best when you model things that don't exist in reality, but only as software concepts, for example, an AbstractList, Buffer or GUI component.

haglin

قبل 10 أشهرdiscuss

It would be in the "Files changed" section on GitHub, not in the git history. If you don't want to see the context, you can turn it off.

haglin

قبل 10 أشهرdiscuss

Splitting up a PR is a lot of work, especially if you want each commit to compile, but it would be great if you could categorize changes using 5–10 colors and then have checkboxes that you can toggle to hide code corresponding to a color.

What each color means would depend on the PR, but, for instance, yellow = refactoring, brown = test code, blue = drive-by fix, orange = more efficient data structure etc.

The colors and their meanings could be set by either the author or the reviewers. It would be similar to the file checkboxes that exist today, but in this case, it would be per concept, not per file.

haglin

السنة الماضيةdiscuss

Yeah, Windows 2000 was probably the best operating system Microsoft ever produced. It had no crashes, a snappy/intuitive/sleek user interface, and DirectX support for games. I am currently running Mac OS X because I never liked Windows XP/Vista/10/11.

In hindsight, the progress Microsoft made in the ten years between Windows 3.0 (1990) and Windows 2000 seems incredible. They transitioned from a 16-bit shell running on top of DOS to a fully-fledged operating system with a hardware abstraction layer, preemptive multitasking, permissions, a registry, proper device drivers etc.

Twenty-five years later, there has been basically no progress.

At a minimum, I would have expected something like the Knowledge Navigator

https://www.youtube.com/watch?v=umJsITGzXd0

haglin

السنة الماضيةdiscuss

Since JDK 11 (released in 2018).

"Launch Single-File Source-Code Programs" https://openjdk.org/jeps/330

haglin

قبل سنتينdiscuss

JFR only samples running Java methods.

I would guess at least some of the bottlenecks are in hardware, the operating system or in native code (including the JVM) in this case.

haglin

قبل سنتينdiscuss

"Left unquestioned, assumptions and expectations could have caused us to miss one of the most impactful changes we’ve made to our operational defaults in a decade"

haglin

قبل 3 سنواتdiscuss

> the only knock you can put on Java for reliability is null-safety

FWIW, nullity control has been added to the Valhalla project, so it might be fixed going forward.

https://youtu.be/Ma0NtbG0mHY?feature=shared&t=1076

haglin

قبل 3 سنواتdiscuss

Two years it too short.

The reason I now use gmail and not hotmail is because Microsoft did a similar thing 20 years ago. When I lost my hotmail account, I thought I might as well use gmail from now on. Reason I didn't log into my hotmail account was because I used the mail address I got from the university.

haglin

قبل 3 سنواتdiscuss

An alternative to avoid safepoints (only samples executing threads)

    var r = new RecordingStream();
    r.enable("jdk.ExecutionSample").withStackTrace().withPeriod(Duration.ofMillis(1));
    r.onEvent("jdk.ExecutionSample", e -> {
        store.addSample(e.getStackTrace().getFrames());
    });   
    r.startAsync();
    ...

haglin

قبل 4 سنواتdiscuss

There are multiple ways to represent an optional value, for example:

1) an empty list/array 2) throw an exception if the return value is missing. 3) -1

Optional can be used as a better alternative in all these cases. It's not just null.

haglin

قبل 5 سنواتdiscuss

Hotspot has sub-millisecond GC pause times.

"But as long as your system isn’t heavily over-provisioned, you can expect to see average GC pause times of around 0.05ms (50µs) and max pause times of around 0.5ms (500µs)." https://malloc.se/blog/zgc-jdk16

haglin

قبل 5 سنواتdiscuss

And in JDK 16, ZGC has concurrent thread-stack processing, which typically reduces GC pauses below 1 ms

https://openjdk.java.net/jeps/376

https://youtu.be/88E86quLmQA?t=1525

haglin

قبل 6 سنواتdiscuss

The JDK comes with a powerful memory leak tool.

$ java -XX:StartFlightRecording:settings=profile MyApp

$ jcmd MyApp JFR.dump paths-to-gc-root=true filename=dump.jfr

$ jfr print --events OldObjectSample --stack-depth 64 dump.jfr

The tool will list objects on the heap, their path to the GC roots and allocation stack trace. That is usually sufficient to solve the memory leak. No need to create a large HPROF file or upload data to a server. Everything can be done in the shell.

https://docs.oracle.com/en/java/javase/13/troubleshoot/troub...

Sensitive information, like credit card numbers, will not even leave the Java heap.

haglin

قبل 7 سنواتdiscuss

In JDK 14, Flight Recorder events will be available for monitoring.

   try (var rs = new RecordingStream()) {
     rs.onEvent("jdk.GCPhasePause", event -> {
       System.out.println(event.getDuration());
     });
   }

haglin

قبل 7 سنواتdiscuss

New IO.

haglin

قبل 7 سنواتdiscuss

I haven't tried serverless, but shouldn't that be Java's cup of tea?

The JVM can load code dynamically and adapt the runtime to the work load. Maybe there is a framework missing, so those that provide serverless starts a new JVM per function call, but they shouldn't really have to do that.

haglin

قبل 7 سنواتdiscuss

For arbitrage that must happen really fast, FPGAs is the way to go, and for complex code that needs to be rewritten often and quickly, Java is probably a better fit than C++.

haglin

قبل 7 سنواتdiscuss

If you want to sell software or services to the government you need to be 508 compliant

https://www.section508.gov/sell

Submissions

JEP 349: JFR Event Streaming Targeted (Java)

JEP 328: Flight Recorder

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