RFR (S): JEP-142: Reduce Cache Contention on Specified Fields

[Doug Lea]

On 11/26/12 13:40, Aleksey Shipilev wrote:
> On 11/26/2012 09:35 PM, Remi Forax wrote:
>> On 11/26/2012 05:44 PM, Aleksey Shipilev wrote:
>>> On 11/26/2012 08:22 PM, Doug Lea wrote:
>>>> One small suggestion to slightly appease the nanny-state folks.
>>>> How about burying the annotation one lever deeper to
>>>> java.util.concurrent.atomic.
>>
>> +1
>>
>
> Still fail to see the rationale about this.

All things considered, I'm back to agreeing with you --
Just j.u.c.Contended

>
>> I think you should re-write the javadoc ...

The Contended.java file and its javadoc in Aleksey's webrev is just a
placeholder to get things moving. We expect to solicit
reviews in the usual way (mainly on concurrency-interest list)
for a version that will make it into JDK8.

>
> I.e.
>
>      @Contended
>      public class ValueClass {
>           private int field1;
>           private int field2;
>           private int field3;
>           private int field4;
>      }
>
> is the shortcut for:
>
>      public class ValueClass {
>           @Contended("theSame") private int field1;
>           @Contended("theSame") private int field2;
>           @Contended("theSame") private int field3;
>           @Contended("theSame") private int field4;
>      }
>
> That is, all the fields would be densely-packed, but will be padded as
> the group. Note that it is not the same as:
>
>      public class ValueClass {
>           @Contended private int field1;
>           @Contended private int field2;
>           @Contended private int field3;
>           @Contended private int field4;
>      }
>
> Maybe that is already confusing enough to drop class-level annotation?
> What do others feel about this?

I think that the most common and most-recommended case will be class-level,
so it should be kept. We can work on the usage advice in the javadocs.

-Doug