Performance improvement to unchecked segment ofNativeRestricted

[Maurizio Cimadamore]

I think the fundamental idea is solid, and I agree there's room to 
improve performance here, but as Ty notes, having a NULL scope might be 
problematic. I think it would perhaps be better to have a 
constant/stateless, always open scope, whose checkValidState method does 
nothing? If that scope is stored in a final static constant, I believe 
C2 will not have many problems in eliminating the overhead of the scope 
check.

Maurizio

On 06/01/2021 01:59, Ty Young wrote:
>
> You may also need to override checkValidState from 
> AbstractMemorySegmentImpl in EverythingSegment. checkValidState calls 
> the scope's checkValidState and since scope is null, you'll get a NPE. 
> The list of methods that call checkValidState include:
>
>
> splitterator
>
> mismatch
>
> address
>
> handoff
>
> share
>
> registerCleaner
>
> close
>
>
> In short, if you do basically anything but simply read/write via 
> VarHandle, including native library usage which uses address(), you're 
> going to get a NPE.
>
>
>
> On 1/5/21 4:32 PM, Radosław Smogura wrote:
>> Hi all,
>>
>> I hope you have a good day.
>>
>> Here I would like to present some changes to increase performance of 
>> ofNativeRestricted - my benchmarks - where I tried to simulate access 
>> from code - outpaced the access to Java array (as intended). As it 
>> looks like that pull request flow has changed, I have to sign-up OCA 
>> (and if this change is fine I would be happy to do this).
>>
>> Below please find benchmark results and link to "pending PR" / branch
>>
>> The results outpaced the Java array access.
>>
>> Benchmark                           Mode  Cnt Score          Error  
>> Units
>> AccessBenchmark.foreignAddress     thrpt    4  86860188.499 ± 
>> 13454393.406  ops/s
>> AccessBenchmark.foreignAddressRaw  thrpt    4  96150181.668 ± 
>> 7025145.700  ops/s
>> AccessBenchmark.target             thrpt    4  93673099.539 ± 
>> 23272596.145  ops/s```
>>
>> versus tests on original repo
>>
>> Benchmark                           Mode  Cnt Score         Error  Units
>> AccessBenchmark.foreignAddress     thrpt    4  81907199.092 ± 
>> 2663269.652  ops/s
>> AccessBenchmark.foreignAddressRaw  thrpt    4  83629168.611 ± 
>> 1025857.535  ops/s
>> AccessBenchmark.target             thrpt    4  94023553.582 ± 
>> 6128411.421  ops/s
>>
>> https://github.com/openjdk/panama-foreign/pull/431
>> [https://avatars2.githubusercontent.com/u/41768318?s=400&v=4]<https://github.com/openjdk/panama-foreign/pull/431> 
>>
>> [WIP] Performance improvement to unchecked segment ofNativeRestricted 
>> by rsmogura · Pull Request #431 · 
>> openjdk/panama-foreign<https://github.com/openjdk/panama-foreign/pull/431>
>> Here's a proposition to tune the access to global scope. This 
>> changes, could help to outpace the access to Java arrays using [] 
>> operator. The results outpaced the Java array access. Benchmark ...
>> github.com
>>
>> Kind regards,
>> Rado