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Java 21 virtual threads #398

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Java 21 virtual threads #398

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eivanov89
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@eivanov89 eivanov89 commented Nov 26, 2023 •
edited by bpkroth
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This patch adds an option "vt" to use virtual threads instead of real OS threads (#395).

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bpkroth commented Dec 1, 2023

Can you please separate out the switch to java 21?

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bpkroth commented Dec 1, 2023

Looks like this needs to come after #399 as well.

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eivanov89 commented Dec 4, 2023 •
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Looks like this needs to come after #399 as well.

I'm sorry, that is my fault. I've just pushed clean branch now.

bpkroth
bpkroth reviewed Dec 5, 2023
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@bpkroth bpkroth mentioned this pull request Dec 7, 2023
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bpkroth added a commit that referenced this pull request Dec 13, 2023
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Upgrade to Java 21 (#410)
b4b3668 
Separates a conversion to Java 21 from #398 and also handles errors
encountered in #369.
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bpkroth reviewed Dec 13, 2023
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src/main/java/com/oltpbenchmark/DBWorkload.java Outdated
@@ -87,6 +87,11 @@ public static void main(String[] args) throws Exception {
intervalMonitor = Integer.parseInt(argsLine.getOptionValue("im"));
}

Boolean useVirtualThreads = false;
if (argsLine.hasOption("vt")) {
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Can you add a long form --virtual-threads option as well?

Please also make sure the --help output is updated.

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@eivanov89 eivanov89 Dec 14, 2023 •
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Ouch, I forgot to add the option at all. Done now:

usage: benchbase
...
 -vt,--virtual-threads <arg>    Use virtual threads instead of real
                                threads

@bpkroth bpkroth linked an issue Dec 14, 2023 that may be closed by this pull request
Consider using Java >= 21 to allow usage of virtual threads #395
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bpkroth commented Dec 14, 2023 •
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@eivanov89 #416 and others made a bunch of changes to the repo at large. Can you please rebase against and updated main and resolve the conflicts?

If you're using the devcontainer for development, you'll probably want to rebuild it too.

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@bpkroth sure, pushed the rebased branch.

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bpkroth commented Dec 15, 2023

@bpkroth sure, pushed the rebased branch.

Looks like it's still got conflicts listed.

Also, can you please think about a way to add tests for this feature?

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@bpkroth sure, pushed the rebased branch.

Looks like it's still got conflicts listed.

I'm sorry for this. Forgot that my main is fork's main :) This time, did the proper rebase.

Also, can you please think about a way to add tests for this feature?

Unfortunately I don't have enough time to work on this further. Also, the feature depends on DB client implementation. For example, I use postgres + c3p0 patch + vthreads. There was a deadlock:

  • we get session for each TPC-C transaction.
  • c3p0 has a session pool limited in size
  • session holders do network I/O. And network I/O frees carrier thread until virtual thread is ready to execute
  • when there're no sessions available, c3p0 calls Object.wait(), which blocks carrier thread
  • benchbase ended in situation, when all carrier threads are blocked by Object.wait()

Your vanilla postgres impl should work though. I fixed our version by adding a sessions semaphore (waiting on it doesn't block carrier thread), so that c3p0 never calls Object.wait(). I'll check if I can bring patch with c3p0 and the semaphore. c3p0 looks like a very useful addition.

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bpkroth commented Dec 15, 2023

@bpkroth sure, pushed the rebased branch.

Looks like it's still got conflicts listed.

I'm sorry for this. Forgot that my main is fork's main :) This time, did the proper rebase.

Also, can you please think about a way to add tests for this feature?

Unfortunately I don't have enough time to work on this further. Also, the feature depends on DB client implementation. For example, I use postgres + c3p0 patch + vthreads. There was a deadlock:

  • we get session for each TPC-C transaction.
  • c3p0 has a session pool limited in size
  • session holders do network I/O. And network I/O frees carrier thread until virtual thread is ready to execute
  • when there're no sessions available, c3p0 calls Object.wait(), which blocks carrier thread
  • benchbase ended in situation, when all carrier threads are blocked by Object.wait()

Your vanilla postgres impl should work though. I fixed our version by adding a sessions semaphore (waiting on it doesn't block carrier thread), so that c3p0 never calls Object.wait(). I'll check if I can bring patch with c3p0 and the semaphore. c3p0 looks like a very useful addition.

Sounds good. We're happy to take a PR for both, but it's always good to have a test associated with new features to make sure we continue to support them in the future and they don't break existing functionality.

@eivanov89 eivanov89 closed this Feb 6, 2024
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I had missed the point, that there are a lot of synchronized inside the benchmark, which should be rewritten at first.

@bpkroth bpkroth mentioned this pull request Mar 20, 2024
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Consider using Java >= 21 to allow usage of virtual threads
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