RFR (S) : JDK-8245043 : Simplified contention benchmark

[Sergey Kuksenko]

On 5/18/20 4:35 PM, David Holmes wrote:
> On 19/05/2020 8:38 am, Sergey Kuksenko wrote:
>> 2. Does "volatile Table[] sharedLocks" need to be volatile?
>
> I think the intent is that the array needs to be published safely - 
> though without knowing full details of JMH it is impossible to see how 
> the array creation and filling relates to threads being started (ie 
> does setup() happen-before any threads are started? If so then 
> publication is already safe.) But if the intent is to do safe 
> publication then refreshArray is wrong:
>
>   85     void refreshArray() {
>   86         sharedLocks = new Table[locksSize];
>   87         for (int i = 0; i < locksSize; i++) {
>   88             sharedLocks[i] = new Table(i);
>   89         }
>   90     }
>
> you would need to create a tmp array and fill it, then assign to 
> sharedLocks with the volatile write that publishes the array.

JMH does safe publication between @Setup and @Benchmark methods. And 
yes, I was asking -  because of either volatile is not required or tmp 
local array reference is required.