RFR: 8347408: Create an internal method handle adapter for system calls with errno [v6]

[Shaojin Wen]

On Tue, 29 Apr 2025 12:33:34 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> 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 ove...
>
> Per Minborg has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add hashCode/equals to record to improve startup time

src/java.base/share/classes/java/lang/foreign/SegmentAllocator.java line 726:

> 724:         return this instanceof NoInitSegmentAllocator noInit ?
> 725:                 noInit.allocateNoInit(byteSize, 1) :
> 726:                 allocate(byteSize);

Suggestion:

        return this instanceof NoInitSegmentAllocator noInit
                ? noInit.allocateNoInit(byteSize, 1) 
                : allocate(byteSize);

How about a different coding style?

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/23765#discussion_r2071659669