RFR: 8347408: Create an internal method handle adapter for system calls with errno [v4]
Per Minborg
pminborg at openjdk.org
Mon Feb 10 14:27:28 UTC 2025
> Going forward, 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 to add 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:
>
>
> Benchmark Mode Cnt Score Error Units
> CaptureStateUtilBench.OfVirtual.adaptedSysCallFail avgt 30 24.193 ? 0.268 ns/op
> CaptureStateUtilBench.OfVirtual.adaptedSysCallSuccess avgt 30 8.268 ? 0.080 ns/op
> CaptureStateUtilBench.OfVirtual.explicitAllocationFail avgt 30 42.076 ? 1.003 ns/op
> CaptureStateUtilBench.OfVirtual.explicitAllocationSuccess avgt 30 21.801 ? 0.138 ns/op
> CaptureStateUtilBench.OfVirtual.tlAllocationFail avgt 30 23.265 ? 0.087 ns/op
> CaptureStateUtilBench.OfVirtual.tlAllocationSuccess avgt 30 8.285 ? 0.155 ns/op
>
> CaptureStateUtilBench.adaptedSysCallFail avgt 30 23.033 ? 0.423 ns/op
> CaptureStateUtilBench.adaptedSysCallSuccess avgt 30 3.676 ? 0.104 ns/op // <- Happy path using an internal pool
>
> CaptureStateUtilBench.explicitAllocationFail avgt 30 42.023 ? 0.736 ns/op
> CaptureStateUtilBench.explicitAllocationSuccess avgt 30 22.013 ? 0.648 ns/op // <- Allocating memory upon each invocation
>
> CaptureStateUtilBench.tlAllocationFail avgt 30 22.050 ? 0.233 ns/op
> CaptureStateUtilBench.tlAllocationSuccess avgt 30 3.756 ? 0.056 ns/op // <- Using the pool explicitly from Java code
>
>
> 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 ~6x performanc...
Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
Add test
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/23517/files
- new: https://git.openjdk.org/jdk/pull/23517/files/0e65ea5b..2fb7af12
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=23517&range=03
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=23517&range=02-03
Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
Patch: https://git.openjdk.org/jdk/pull/23517.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/23517/head:pull/23517
PR: https://git.openjdk.org/jdk/pull/23517
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