On Fri, 7 Feb 2025 14:46:06 GMT, Per Minborg <[email protected]> wrote:
> 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...
This pull request has been closed without being integrated.
-------------
PR: https://git.openjdk.org/jdk/pull/23517
