[foreign-memaccess+abi] RFR: Performance improvement to unchecked segment ofNativeRestricted [v2]

[Maurizio Cimadamore]

On Thu, 14 Jan 2021 23:24:23 GMT, Radoslaw Smogura <github.com+7535718+rsmogura at openjdk.org> wrote:

>> This changes removes (by making no-ops) range and temporal checks for `ofNativeRestricted` segment. As this segment is global, above checks are not needed.
>> 
>> Generated native code is smaller, and execution outperforms Java native arrays (depending on CPU)
>> Changed
>> Benchmark                           Mode  Cnt          Score        Error  Units
>> AccessBenchmark.foreignAddress     thrpt    5  128946129.691 ± 317433.113  ops/s
>> AccessBenchmark.foreignAddressRaw  thrpt    5  136883439.221 ± 749390.255  ops/s
>> AccessBenchmark.target             thrpt    5  125325586.957 ±  32129.931  ops/s
>> Base
>> Benchmark                           Mode  Cnt          Score        Error  Units
>> AccessBenchmark.foreignAddress     thrpt    5  125257424.876 ± 230508.169  ops/s
>> AccessBenchmark.foreignAddressRaw  thrpt    5  128818591.434 ± 241806.765  ops/s
>> AccessBenchmark.target             thrpt    5  125083379.819 ± 184070.467  ops/s
>> ---
>> This PR is replacement for https://github.com/openjdk/panama-foreign/pull/431 (OCA)
>> and was partially discussed (before changes) in https://mail.openjdk.java.net/pipermail/panama-dev/2021-January/011747.htm
>> 
>> ---
>> Benchmark
>> @State(Scope.Thread)
>> public class AccessBenchmark {
>>     static final MemorySegment ms = MemorySegment.ofNativeRestricted();
>>     static final VarHandle intHandle = MemoryHandles.varHandle(int.class, ByteOrder.nativeOrder());
>> 
>>     int[] intData = new int[12];
>>     volatile int intDataOffset = 0;
>> 
>>     volatile MemoryAddress address;
>>     volatile long addressRaw;
>> 
>>     @Setup
>>     public void setup() {
>>         var ms = MemorySegment.allocateNative(256);
>>         address = ms.address();
>>         addressRaw = address.toRawLongValue();
>>     }
>> 
>>     @Benchmark
>>     public void target(Blackhole bh) {
>>         int[] local = intData;
>>         int localOffset = intDataOffset;
>>         bh.consume(local[localOffset]);
>>         bh.consume(local[localOffset + 1]);
>>     }
>> 
>>     @Benchmark
>>     public void foreignAddress(Blackhole bh) {
>>         var a = address;
>>         bh.consume((int) intHandle.get(ms, a.addOffset(0).toRawLongValue()));
>>         bh.consume((int) intHandle.get(ms, a.addOffset(4).toRawLongValue()));
>>     }
>> 
>>     @Benchmark
>>     public void foreignAddressRaw(Blackhole bh) {
>>         var a = addressRaw;
>>         bh.consume((int) intHandle.get(ms, a));
>>         bh.consume((int) intHandle.get(ms, a + 4));
>>     }
>> }
>
> Radoslaw Smogura has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.

Looks good! Thanks for investigating the issues with lack of static on Unsafe.

Could we please add the benchmark under test/micro/org/openjdk/bench/jdk/incubator/foreign ? We try to add benchmark for each case we find as we go along, to make sure we don't regress. This seems like another interesting case.

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PR: https://git.openjdk.java.net/panama-foreign/pull/437