> 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 currently relies on a thread-local cache of MemorySegments to allide > allocations. If, in the future, a more efficient thread-associated allocation > scheme becomes available, we could easily migrate to that one. > > Here are some benchmarks: > > > Benchmark Mode Cnt Score Error > Units > CaptureStateUtilBench.explicitAllocationFail avgt 30 43.942 ? 2.425 > ns/op > CaptureStateUtilBench.explicitAllocationSuccess avgt 30 23.606 ? 0.837 > ns/op > CaptureStateUtilBench.threadLocalFail avgt 30 15.660 ? 0.073 > ns/op > CaptureStateUtilBench.threadLocalReuseSuccess avgt 30 12.712 ? 0.407 > ns/op > > > Explicit allocation: > > try (var arena = Arena.ofConfined()) { > return (int) HANDLE.invoke(arena.allocate(4), 0, 0); > } > > > Thread Local (tl): > > return (int) ADAPTED_HANDLE.invoke(arena.allocate(4), 0, 0); > > > The graph below shows the difference in latency for a successful call: > >  > > This is a ~2x improvement on the happy path. > > > Tested and passed tiers 1-3.
Per Minborg has updated the pull request incrementally with two additional commits since the last revision: - Remove unused classes - Remove blanks ------------- Changes: - all: https://git.openjdk.org/jdk/pull/22391/files - new: https://git.openjdk.org/jdk/pull/22391/files/3b8723f3..090ffb6d Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=22391&range=10 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22391&range=09-10 Stats: 361 lines in 3 files changed: 0 ins; 360 del; 1 mod Patch: https://git.openjdk.org/jdk/pull/22391.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/22391/head:pull/22391 PR: https://git.openjdk.org/jdk/pull/22391