RFR: 8347408: Create an internal method handle adapter for system calls with errno [v3]
Per Minborg
pminborg at openjdk.org
Thu Mar 13 15:21:33 UTC 2025
> As we advance, converting older JDK code to use the relatively new FFM API requires system calls that can provide `errno` and the likes to explicitly allocate a `MemorySegment` to capture potential error states. This can lead to negative performance implications if not designed carefully and also introduces unnecessary code complexity.
>
> Hence, this PR proposes adding a JDK internal method handle adapter that can be used to handle system calls with `errno`, `GetLastError`, and `WSAGetLastError`.
>
> It relies on an efficient carrier-thread-local cache of memory regions to allide allocations.
>
>
> Here are some benchmarks that ran on a platform thread and virtual threads respectively (M1 Mac):
>
>
> Benchmark Mode Cnt Score Error Units
> CaptureStateUtilBench.OfVirtual.adaptedSysCallFail avgt 30 24.330 ? 0.820 ns/op
> CaptureStateUtilBench.OfVirtual.adaptedSysCallSuccess avgt 30 8.257 ? 0.117 ns/op
> CaptureStateUtilBench.OfVirtual.explicitAllocationFail avgt 30 41.415 ? 1.013 ns/op
> CaptureStateUtilBench.OfVirtual.explicitAllocationSuccess avgt 30 21.720 ? 0.463 ns/op
> CaptureStateUtilBench.OfVirtual.tlAllocationFail avgt 30 23.636 ? 0.182 ns/op
> CaptureStateUtilBench.OfVirtual.tlAllocationSuccess avgt 30 8.234 ? 0.156 ns/op
> CaptureStateUtilBench.adaptedSysCallFail avgt 30 23.918 ? 0.487 ns/op
> CaptureStateUtilBench.adaptedSysCallSuccess avgt 30 4.946 ? 0.089 ns/op
> CaptureStateUtilBench.explicitAllocationFail avgt 30 42.280 ? 1.128 ns/op
> CaptureStateUtilBench.explicitAllocationSuccess avgt 30 21.809 ? 0.413 ns/op
> CaptureStateUtilBench.tlAllocationFail avgt 30 24.422 ? 0.673 ns/op
> CaptureStateUtilBench.tlAllocationSuccess avgt 30 5.182 ? 0.152 ns/op
>
>
> Adapted system call:
>
> return (int) ADAPTED_HANDLE.invoke(0, 0); // Uses a MH-internal pool
> ```
> Explicit allocation:
>
> try (var arena = Arena.ofConfined()) {
> return (int) HANDLE.invoke(arena.allocate(4), 0, 0);
> }
> ```
> Thread Local allocation:
>
> try (var arena = POOLS.take()) {
> return (int) HANDLE.invoke(arena.allocate(4), 0, 0); // Uses a manually specified pool
> }
> ```
> The adapted system call exhibits a ~4x performance improvement over the existing "explicit allocation" scheme for the happy path on platform threads. ...
Per Minborg has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 34 commits:
- Merge master
- Add test for woven allocation
- Merge branch 'master' into errno-util3
- Use lazy initialization of method handles
- Clean up visibility
- Merge branch 'master' into errno-util3
- Add @ForceInline annotations
- Add out of order test for VTs
- Allow memory reuse for several arenas
- Remove file
- ... and 24 more: https://git.openjdk.org/jdk/compare/4e51a8c9...6d782a84
-------------
Changes: https://git.openjdk.org/jdk/pull/23765/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23765&range=02
Stats: 1913 lines in 13 files changed: 1901 ins; 2 del; 10 mod
Patch: https://git.openjdk.org/jdk/pull/23765.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/23765/head:pull/23765
PR: https://git.openjdk.org/jdk/pull/23765
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